Major updates in preparation for 3.80.

New version of the manual, put into the doc subdir.
Enhancements: $(eval ...) and $(value ...) functions, various bug
fixes, etc.  See the ChangeLog.
More to come.

2 files changed, 10170 insertions, 0 deletions

diff --git a/doc/Makefile.am b/doc/Makefile.am
new file mode 100644
index 0000000..bf979c8
--- /dev/null
+++ b/doc/Makefile.am
@@ -0,0 +1,29 @@
+## Process this file with automake to create Makefile.in.
+
+## Makefile for GNU make documentation.
+## Copyright 2002 Free Software Foundation, Inc.
+
+TEXI2HTML = texi2html
+TEXI2HTML_FLAGS = -split_chapter
+
+info_TEXINFOS =	make.texi
+make_TEXINFOS = fdl.texi make-stds.texi
+
+CLEANFILES = make*.html make*.pdf
+
+## ----------------------------- ##
+## Other documentation formats.  ##
+## ----------------------------- ##
+
+html: make_1.html
+
+make_1.html: $(info_TEXINFOS) $(make_TEXINFOS)
+	$(TEXI2HTML) $(TEXI2HTML_FLAGS) $(srcdir)/make.texi
+
+
+pdf: make.pdf
+
+make.pdf: $(info_TEXINFOS) $(make_TEXINFOS)
+	$(TEXI2DVI) --pdf --batch $(srcdir)/make.texi
+
+.PHONY: html pdf
diff --git a/doc/make.texi b/doc/make.texi
new file mode 100644
index 0000000..20fc1c8
--- /dev/null
+++ b/doc/make.texi
@@ -0,0 +1,10141 @@
+\input texinfo                @c -*- Texinfo -*-
+@c %**start of header
+@setfilename make.info
+@settitle GNU @code{make}
+@setchapternewpage odd
+@c %**end of header
+
+@c FSF publishers: format makebook.texi instead of using this file directly.
+
+@set RCSID $Id$
+@set EDITION 0.60
+@set VERSION 3.80
+@set UPDATED 08 July 2002
+@set UPDATE-MONTH July 2002
+@comment The ISBN number might need to change on next publication.
+@set ISBN 1-882114-81-7 @c From Brian Youmans <3diff@gnu.org>, 25 Apr 2000
+
+@c finalout
+
+@c ISPELL CHECK: done, 10 June 1993 --roland
+@c ISPELL CHECK: done, 2000-06-25 --Martin Buchholz
+
+@c Combine the variable and function indices:
+@syncodeindex vr fn
+@c Combine the program and concept indices:
+@syncodeindex pg cp
+
+@dircategory GNU Packages
+@direntry
+* Make: (make).            Remake files automatically.
+@end direntry
+
+@ifinfo
+This file documents the GNU Make utility, which determines
+automatically which pieces of a large program need to be recompiled,
+and issues the commands to recompile them.
+
+This is Edition @value{EDITION}, last updated @value{UPDATED},
+of @cite{The GNU Make Manual}, for @code{make}, Version @value{VERSION}.
+
+Copyright 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2002
+Free Software Foundation, Inc.
+
+Permission is granted to copy, distribute and/or modify this document
+under the terms of the GNU Free Documentation License, Version 1.1 or
+any later version published by the Free Software Foundation; with no
+Invariant Sections, with no Front-Cover Texts, and with no Back-Cover
+Texts.  A copy of the license is included in the section entitled
+``GNU Free Documentation License''.
+@end ifinfo
+
+@iftex
+@shorttitlepage GNU Make
+@end iftex
+@titlepage
+@title GNU Make
+@subtitle A Program for Directing Recompilation
+@subtitle GNU @code{make} Version @value{VERSION}
+@subtitle @value{UPDATE-MONTH}
+@author Richard M. Stallman, Roland McGrath, Paul Smith
+@page
+@vskip 0pt plus 1filll
+Copyright @copyright{} 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995,
+1996, 1997, 1998, 1999, 2000, 2002 Free Software Foundation, Inc.
+@sp 2
+Published by the Free Software Foundation @*
+59 Temple Place -- Suite 330, @*
+Boston, MA 02111-1307 USA @*
+ISBN @value{ISBN} @*
+
+Maintenance and updates since Version 3.76 by Paul D. Smith.
+
+Permission is granted to copy, distribute and/or modify this document
+under the terms of the GNU Free Documentation License, Version 1.1 or
+any later version published by the Free Software Foundation; with no
+Invariant Sections, with no Front-Cover Texts, and with no Back-Cover
+Texts.  A copy of the license is included in the section entitled
+``GNU Free Documentation License''.
+@sp 2
+Cover art by Etienne Suvasa.
+@end titlepage
+@page
+
+@ifinfo
+@node Top, Overview, (dir), (dir)
+@top Make
+
+The GNU @code{make} utility automatically determines which pieces of a
+large program need to be recompiled, and issues the commands to
+recompile them.@refill
+
+This edition of the @cite{GNU Make Manual},
+last updated @value{UPDATED},
+documents GNU @code{make} Version @value{VERSION}.@refill
+
+This manual describes @code{make} and contains the following chapters:@refill
+@end ifinfo
+
+@menu
+* Overview::                    Overview of @code{make}.
+* Introduction::                An introduction to @code{make}.
+* Makefiles::                   Makefiles tell @code{make} what to do.
+* Rules::                       Rules describe when a file must be remade.
+* Commands::                    Commands say how to remake a file.
+* Using Variables::             You can use variables to avoid repetition.
+* Conditionals::                Use or ignore parts of the makefile based
+                                  on the values of variables.
+* Functions::                   Many powerful ways to manipulate text.
+* Invoking make: Running.       How to invoke @code{make} on the command line.
+* Implicit Rules::              Use implicit rules to treat many files alike,
+                                  based on their file names.
+* Archives::                    How @code{make} can update library archives.
+* Features::                    Features GNU @code{make} has over other @code{make}s.
+* Missing::                     What GNU @code{make} lacks from other @code{make}s.
+* Makefile Conventions::        Conventions for writing makefiles for
+                                  GNU programs.
+* Quick Reference::             A quick reference for experienced users.
+* Error Messages::              A list of common errors generated by @code{make}.
+* Complex Makefile::            A real example of a straightforward,
+                                  but nontrivial, makefile.
+
+* GNU Free Documentation License::  License for copying this manual
+* Concept Index::               Index of Concepts
+* Name Index::                  Index of Functions, Variables, & Directives
+
+@detailmenu
+ --- The Detailed Node Listing ---
+
+Overview of @code{make}
+
+* Preparing::                   Preparing and Running Make
+* Reading::                     On Reading this Text
+* Bugs::                        Problems and Bugs
+
+An Introduction to Makefiles
+
+* Rule Introduction::           What a rule looks like.
+* Simple Makefile::             A Simple Makefile
+* How Make Works::              How @code{make} Processes This Makefile
+* Variables Simplify::          Variables Make Makefiles Simpler
+* make Deduces::                Letting @code{make} Deduce the Commands
+* Combine By Prerequisite::     Another Style of Makefile
+* Cleanup::                     Rules for Cleaning the Directory
+
+Writing Makefiles
+
+* Makefile Contents::           What makefiles contain.
+* Makefile Names::              How to name your makefile.
+* Include::                     How one makefile can use another makefile.
+* MAKEFILES Variable::          The environment can specify extra makefiles.
+* MAKEFILE_LIST Variable::      Discover which makefiles have been read.
+* Remaking Makefiles::          How makefiles get remade.
+* Overriding Makefiles::        How to override part of one makefile
+                                  with another makefile.
+* Reading Makefiles::           How makefiles are parsed.
+
+Writing Rules
+
+* Rule Example::                An example explained.
+* Rule Syntax::                 General syntax explained.
+* Wildcards::                   Using wildcard characters such as `*'.
+* Directory Search::            Searching other directories for source files.
+* Phony Targets::               Using a target that is not a real file's name.
+* Force Targets::               You can use a target without commands
+                                  or prerequisites to mark other
+                                  targets as phony.
+* Empty Targets::               When only the date matters and the
+                                  files are empty.
+* Special Targets::             Targets with special built-in meanings.
+* Multiple Targets::            When to make use of several targets in a rule.
+* Multiple Rules::              How to use several rules with the same target.
+* Static Pattern::              Static pattern rules apply to multiple targets
+                                  and can vary the prerequisites according to
+                                  the target name.
+* Double-Colon::                How to use a special kind of rule to allow
+                                  several independent rules for one target.
+* Automatic Prerequisites::     How to automatically generate rules giving
+                                  prerequisites from source files themselves.
+
+Using Wildcard Characters in File Names
+
+* Wildcard Examples::           Several examples
+* Wildcard Pitfall::            Problems to avoid.
+* Wildcard Function::           How to cause wildcard expansion where
+                                  it does not normally take place.
+
+Searching Directories for Prerequisites
+
+* General Search::              Specifying a search path that applies
+                                  to every prerequisite.
+* Selective Search::            Specifying a search path
+                                  for a specified class of names.
+* Search Algorithm::            When and how search paths are applied.
+* Commands/Search::             How to write shell commands that work together
+                                  with search paths.
+* Implicit/Search::             How search paths affect implicit rules.
+* Libraries/Search::            Directory search for link libraries.
+
+Static Pattern Rules
+
+* Static Usage::                The syntax of static pattern rules.
+* Static versus Implicit::      When are they better than implicit rules?
+
+Writing the Commands in Rules
+
+* Echoing::                     How to control when commands are echoed.
+* Execution::                   How commands are executed.
+* Parallel::                    How commands can be executed in parallel.
+* Errors::                      What happens after a command execution error.
+* Interrupts::                  What happens when a command is interrupted.
+* Recursion::                   Invoking @code{make} from makefiles.
+* Sequences::                   Defining canned sequences of commands.
+* Empty Commands::              Defining useful, do-nothing commands.
+
+Recursive Use of @code{make}
+
+* MAKE Variable::               The special effects of using @samp{$(MAKE)}.
+* Variables/Recursion::         How to communicate variables to a sub-@code{make}.
+* Options/Recursion::           How to communicate options to a sub-@code{make}.
+* -w Option::                   How the @samp{-w} or @samp{--print-directory} option
+                                  helps debug use of recursive @code{make} commands.
+
+How to Use Variables
+
+* Reference::                   How to use the value of a variable.
+* Flavors::                     Variables come in two flavors.
+* Advanced::                    Advanced features for referencing a variable.
+* Values::                      All the ways variables get their values.
+* Setting::                     How to set a variable in the makefile.
+* Appending::                   How to append more text to the old value
+                                  of a variable.
+* Override Directive::          How to set a variable in the makefile even if
+                                  the user has set it with a command argument.
+* Defining::                    An alternate way to set a variable
+                                  to a verbatim string.
+* Environment::                 Variable values can come from the environment.
+* Target-specific::             Variable values can be defined on a per-target
+                                  basis.
+* Pattern-specific::            Target-specific variable values can be applied
+                                  to a group of targets that match a pattern.
+
+Advanced Features for Reference to Variables
+
+* Substitution Refs::           Referencing a variable with
+                                  substitutions on the value.
+* Computed Names::              Computing the name of the variable to refer to.
+
+Conditional Parts of Makefiles
+
+* Conditional Example::         Example of a conditional
+* Conditional Syntax::          The syntax of conditionals.
+* Testing Flags::               Conditionals that test flags.
+
+Functions for Transforming Text
+
+* Syntax of Functions::         How to write a function call.
+* Text Functions::              General-purpose text manipulation functions.
+* File Name Functions::         Functions for manipulating file names.
+* Foreach Function::            Repeat some text with controlled variation.
+* If Function::                 Conditionally expand a value.
+* Call Function::               Expand a user-defined function.
+* Value Function::              Return the un-expanded value of a variable.
+* Eval Function::               Evaluate the arguments as makefile syntax.
+* Origin Function::             Find where a variable got its value.
+* Shell Function::              Substitute the output of a shell command.
+* Make Control Functions::      Functions that control how make runs.
+
+How to Run @code{make}
+
+* Makefile Arguments::          How to specify which makefile to use.
+* Goals::                       How to use goal arguments to specify which
+                                  parts of the makefile to use.
+* Instead of Execution::        How to use mode flags to specify what
+                                  kind of thing to do with the commands
+                                  in the makefile other than simply
+                                  execute them.
+* Avoiding Compilation::        How to avoid recompiling certain files.
+* Overriding::                  How to override a variable to specify
+                                  an alternate compiler and other things.
+* Testing::                     How to proceed past some errors, to
+                                  test compilation.
+* Options Summary::             Summary of Options
+
+Using Implicit Rules
+
+* Using Implicit::              How to use an existing implicit rule
+                                  to get the commands for updating a file.
+* Catalogue of Rules::          A list of built-in implicit rules.
+* Implicit Variables::          How to change what predefined rules do.
+* Chained Rules::               How to use a chain of implicit rules.
+* Pattern Rules::               How to define new implicit rules.
+* Last Resort::                 How to defining commands for rules
+                                  which cannot find any.
+* Suffix Rules::                The old-fashioned style of implicit rule.
+* Implicit Rule Search::        The precise algorithm for applying
+                                  implicit rules.
+
+Defining and Redefining Pattern Rules
+
+* Pattern Intro::               An introduction to pattern rules.
+* Pattern Examples::            Examples of pattern rules.
+* Automatic::                   How to use automatic variables in the
+                                  commands of implicit rules.
+* Pattern Match::               How patterns match.
+* Match-Anything Rules::        Precautions you should take prior to
+                                  defining rules that can match any
+                                  target file whatever.
+* Canceling Rules::             How to override or cancel built-in rules.
+
+Using @code{make} to Update Archive Files
+
+* Archive Members::             Archive members as targets.
+* Archive Update::              The implicit rule for archive member targets.
+* Archive Pitfalls::            Dangers to watch out for when using archives.
+* Archive Suffix Rules::        You can write a special kind of suffix rule
+                                  for updating archives.
+
+Implicit Rule for Archive Member Targets
+
+* Archive Symbols::             How to update archive symbol directories.
+
+Makefile Conventions
+
+* Makefile Basics::             General Conventions for Makefiles
+* Utilities in Makefiles::      Utilities in Makefiles
+* Command Variables::           Variables for Specifying Commands
+* Directory Variables::         Variables for Installation Directories
+* Standard Targets::            Standard Targets for Users
+* Install Command Categories::  Three categories of commands in the `install'
+
+Copying This Manual
+
+@end detailmenu
+@end menu
+
+@node Overview, Introduction, Top, Top
+@comment  node-name,  next,  previous,  up
+@chapter Overview of @code{make}
+
+The @code{make} utility automatically determines which pieces of a large
+program need to be recompiled, and issues commands to recompile them.
+This manual describes GNU @code{make}, which was implemented by Richard
+Stallman and Roland McGrath.  Development since Version 3.76 has been
+handled by Paul Smith.
+
+GNU @code{make} conforms to section 6.2 of @cite{IEEE Standard
+1003.2-1992} (POSIX.2).
+@cindex POSIX
+@cindex IEEE Standard 1003.2
+@cindex standards conformance
+
+Our examples show C programs, since they are most common, but you can use
+@code{make} with any programming language whose compiler can be run with a
+shell command.  Indeed, @code{make} is not limited to programs.  You can
+use it to describe any task where some files must be updated automatically
+from others whenever the others change.
+
+@menu
+* Preparing::                   Preparing and Running Make
+* Reading::                     On Reading this Text
+* Bugs::                        Problems and Bugs
+@end menu
+
+@node Preparing, Reading, Overview, Overview
+@ifinfo
+@heading Preparing and Running Make
+@end ifinfo
+
+To prepare to use @code{make}, you must write a file called
+the @dfn{makefile} that describes the relationships among files
+in your program and provides commands for updating each file.
+In a program, typically, the executable file is updated from object
+files, which are in turn made by compiling source files.@refill
+
+Once a suitable makefile exists, each time you change some source files,
+this simple shell command:
+
+@example
+make
+@end example
+
+@noindent
+suffices to perform all necessary recompilations.  The @code{make} program
+uses the makefile data base and the last-modification times of the files to
+decide which of the files need to be updated.  For each of those files, it
+issues the commands recorded in the data base.
+
+You can provide command line arguments to @code{make} to control which
+files should be recompiled, or how.  @xref{Running, ,How to Run
+@code{make}}.
+
+@node Reading, Bugs, Preparing, Overview
+@section How to Read This Manual
+
+If you are new to @code{make}, or are looking for a general
+introduction, read the first few sections of each chapter, skipping the
+later sections.  In each chapter, the first few sections contain
+introductory or general information and the later sections contain
+specialized or technical information.
+@ifinfo
+The exception is the second chapter, @ref{Introduction, ,An
+Introduction to Makefiles}, all of which is introductory.
+@end ifinfo
+@iftex
+The exception is @ref{Introduction, ,An Introduction to Makefiles},
+all of which is introductory.
+@end iftex
+
+If you are familiar with other @code{make} programs, see @ref{Features,
+,Features of GNU @code{make}}, which lists the enhancements GNU
+@code{make} has, and @ref{Missing, ,Incompatibilities and Missing
+Features}, which explains the few things GNU @code{make} lacks that
+others have.
+
+For a quick summary, see @ref{Options Summary}, @ref{Quick Reference},
+and @ref{Special Targets}.
+
+@node Bugs,  , Reading, Overview
+@section Problems and Bugs
+@cindex reporting bugs
+@cindex bugs, reporting
+@cindex problems and bugs, reporting
+
+If you have problems with GNU @code{make} or think you've found a bug,
+please report it to the developers; we cannot promise to do anything but
+we might well want to fix it.
+
+Before reporting a bug, make sure you've actually found a real bug.
+Carefully reread the documentation and see if it really says you can do
+what you're trying to do.  If it's not clear whether you should be able
+to do something or not, report that too; it's a bug in the
+documentation!
+
+Before reporting a bug or trying to fix it yourself, try to isolate it
+to the smallest possible makefile that reproduces the problem.  Then
+send us the makefile and the exact results @code{make} gave you.  When
+generating this small makefile, be sure to not use any non-free or
+unusual tools in your commands: you can almost always emulate what
+such a tool would do with simple shell commands.  Finally, be sure to
+explain what you expected to occur; this will help us decide whether
+the problem was really in the documentation.
+
+Once you've got a precise problem, please send electronic mail to:
+
+@example
+    bug-make@@gnu.org
+@end example
+
+@noindent
+Please include the version number of @code{make} you are using.  You can
+get this information with the command @samp{make --version}.
+Be sure also to include the type of machine and operating system you are
+using.
+
+@node Introduction, Makefiles, Overview, Top
+@comment  node-name,  next,  previous,  up
+@chapter An Introduction to Makefiles
+
+You need a file called a @dfn{makefile} to tell @code{make} what to do.
+Most often, the makefile tells @code{make} how to compile and link a
+program.
+@cindex makefile
+
+In this chapter, we will discuss a simple makefile that describes how to
+compile and link a text editor which consists of eight C source files
+and three header files.  The makefile can also tell @code{make} how to
+run miscellaneous commands when explicitly asked (for example, to remove
+certain files as a clean-up operation).  To see a more complex example
+of a makefile, see @ref{Complex Makefile}.
+
+When @code{make} recompiles the editor, each changed C source file
+must be recompiled.  If a header file has changed, each C source file
+that includes the header file must be recompiled to be safe.  Each
+compilation produces an object file corresponding to the source file.
+Finally, if any source file has been recompiled, all the object files,
+whether newly made or saved from previous compilations, must be linked
+together to produce the new executable editor.
+@cindex recompilation
+@cindex editor
+
+@menu
+* Rule Introduction::           What a rule looks like.
+* Simple Makefile::             A Simple Makefile
+* How Make Works::              How @code{make} Processes This Makefile
+* Variables Simplify::          Variables Make Makefiles Simpler
+* make Deduces::                Letting @code{make} Deduce the Commands
+* Combine By Prerequisite::     Another Style of Makefile
+* Cleanup::                     Rules for Cleaning the Directory
+@end menu
+
+@node Rule Introduction, Simple Makefile, Introduction, Introduction
+@comment  node-name,  next,  previous,  up
+@section What a Rule Looks Like
+@cindex rule, introduction to
+@cindex makefile rule parts
+@cindex parts of makefile rule
+
+A simple makefile consists of ``rules'' with the following shape:
+
+@cindex targets, introduction to
+@cindex prerequisites, introduction to
+@cindex commands, introduction to
+@example
+@group
+@var{target} @dots{} : @var{prerequisites} @dots{}
+        @var{command}
+        @dots{}
+        @dots{}
+@end group
+@end example
+
+A @dfn{target} is usually the name of a file that is generated by a
+program; examples of targets are executable or object files.  A target
+can also be the name of an action to carry out, such as @samp{clean}
+(@pxref{Phony Targets}).
+
+A @dfn{prerequisite} is a file that is used as input to create the
+target.  A target often depends on several files.
+
+@cindex tabs in rules
+A @dfn{command} is an action that @code{make} carries out.
+A rule may have more than one command, each on its own line.
+@strong{Please note:} you need to put a tab character at the beginning of
+every command line!  This is an obscurity that catches the unwary.
+
+Usually a command is in a rule with prerequisites and serves to create a
+target file if any of the prerequisites change.  However, the rule that
+specifies commands for the target need not have prerequisites.  For
+example, the rule containing the delete command associated with the
+target @samp{clean} does not have prerequisites.
+
+A @dfn{rule}, then, explains how and when to remake certain files
+which are the targets of the particular rule.  @code{make} carries out
+the commands on the prerequisites to create or update the target.  A
+rule can also explain how and when to carry out an action.
+@xref{Rules, , Writing Rules}.
+
+A makefile may contain other text besides rules, but a simple makefile
+need only contain rules.  Rules may look somewhat more complicated
+than shown in this template, but all fit the pattern more or less.
+
+@node Simple Makefile, How Make Works, Rule Introduction, Introduction
+@section A Simple Makefile
+@cindex simple makefile
+@cindex makefile, simple
+
+Here is a straightforward makefile that describes the way an
+executable file called @code{edit} depends on eight object files
+which, in turn, depend on eight C source and three header files.
+
+In this example, all the C files include @file{defs.h}, but only those
+defining editing commands include @file{command.h}, and only low
+level files that change the editor buffer include @file{buffer.h}.
+
+@example
+@group
+edit : main.o kbd.o command.o display.o \
+       insert.o search.o files.o utils.o
+        cc -o edit main.o kbd.o command.o display.o \
+                   insert.o search.o files.o utils.o
+
+main.o : main.c defs.h
+        cc -c main.c
+kbd.o : kbd.c defs.h command.h
+        cc -c kbd.c
+command.o : command.c defs.h command.h
+        cc -c command.c
+display.o : display.c defs.h buffer.h
+        cc -c display.c
+insert.o : insert.c defs.h buffer.h
+        cc -c insert.c
+search.o : search.c defs.h buffer.h
+        cc -c search.c
+files.o : files.c defs.h buffer.h command.h
+        cc -c files.c
+utils.o : utils.c defs.h
+        cc -c utils.c
+clean :
+        rm edit main.o kbd.o command.o display.o \
+           insert.o search.o files.o utils.o
+@end group
+@end example
+
+@noindent
+We split each long line into two lines using backslash-newline; this is
+like using one long line, but is easier to read.
+@cindex continuation lines
+@cindex @code{\} (backslash), for continuation lines
+@cindex backslash (@code{\}), for continuation lines
+@cindex quoting newline, in makefile
+@cindex newline, quoting, in makefile
+
+To use this makefile to create the executable file called @file{edit},
+type:
+
+@example
+make
+@end example
+
+To use this makefile to delete the executable file and all the object
+files from the directory, type:
+
+@example
+make clean
+@end example
+
+In the example makefile, the targets include the executable file
+@samp{edit}, and the object files @samp{main.o} and @samp{kbd.o}.  The
+prerequisites are files such as @samp{main.c} and @samp{defs.h}.
+In fact, each @samp{.o} file is both a target and a prerequisite.
+Commands include @w{@samp{cc -c main.c}} and @w{@samp{cc -c kbd.c}}.
+
+When a target is a file, it needs to be recompiled or relinked if any
+of its prerequisites change.  In addition, any prerequisites that are
+themselves automatically generated should be updated first.  In this
+example, @file{edit} depends on each of the eight object files; the
+object file @file{main.o} depends on the source file @file{main.c} and
+on the header file @file{defs.h}.
+
+A shell command follows each line that contains a target and
+prerequisites.  These shell commands say how to update the target file.
+A tab character must come at the beginning of every command line to
+distinguish commands lines from other lines in the makefile.  (Bear in
+mind that @code{make} does not know anything about how the commands
+work.  It is up to you to supply commands that will update the target
+file properly.  All @code{make} does is execute the commands in the rule
+you have specified when the target file needs to be updated.)
+@cindex shell command
+
+The target @samp{clean} is not a file, but merely the name of an
+action.  Since you
+normally
+do not want to carry out the actions in this rule, @samp{clean} is not a prerequisite of any other rule.
+Consequently, @code{make} never does anything with it unless you tell
+it specifically.  Note that this rule not only is not a prerequisite, it
+also does not have any prerequisites, so the only purpose of the rule
+is to run the specified commands.  Targets that do not refer to files
+but are just actions are called @dfn{phony targets}.  @xref{Phony
+Targets}, for information about this kind of target.  @xref{Errors, ,
+Errors in Commands}, to see how to cause @code{make} to ignore errors
+from @code{rm} or any other command.
+@cindex @code{clean} target
+@cindex @code{rm} (shell command)
+
+@node How Make Works, Variables Simplify, Simple Makefile, Introduction
+@comment  node-name,  next,  previous,  up
+@section How @code{make} Processes a Makefile
+@cindex processing a makefile
+@cindex makefile, how @code{make} processes
+
+By default, @code{make} starts with the first target (not targets whose
+names start with @samp{.}).  This is called the @dfn{default goal}.
+(@dfn{Goals} are the targets that @code{make} strives ultimately to
+update.  @xref{Goals, , Arguments to Specify the Goals}.)
+@cindex default goal
+@cindex goal, default
+@cindex goal
+
+In the simple example of the previous section, the default goal is to
+update the executable program @file{edit}; therefore, we put that rule
+first.
+
+Thus, when you give the command:
+
+@example
+make
+@end example
+
+@noindent
+@code{make} reads the makefile in the current directory and begins by
+processing the first rule.  In the example, this rule is for relinking
+@file{edit}; but before @code{make} can fully process this rule, it
+must process the rules for the files that @file{edit} depends on,
+which in this case are the object files.  Each of these files is
+processed according to its own rule.  These rules say to update each
+@samp{.o} file by compiling its source file.  The recompilation must
+be done if the source file, or any of the header files named as
+prerequisites, is more recent than the object file, or if the object
+file does not exist.
+
+The other rules are processed because their targets appear as
+prerequisites of the goal.  If some other rule is not depended on by the
+goal (or anything it depends on, etc.), that rule is not processed,
+unless you tell @code{make} to do so (with a command such as
+@w{@code{make clean}}).
+
+Before recompiling an object file, @code{make} considers updating its
+prerequisites, the source file and header files.  This makefile does not
+specify anything to be done for them---the @samp{.c} and @samp{.h} files
+are not the targets of any rules---so @code{make} does nothing for these
+files.  But @code{make} would update automatically generated C programs,
+such as those made by Bison or Yacc, by their own rules at this time.
+
+After recompiling whichever object files need it, @code{make} decides
+whether to relink @file{edit}.  This must be done if the file
+@file{edit} does not exist, or if any of the object files are newer than
+it.  If an object file was just recompiled, it is now newer than
+@file{edit}, so @file{edit} is relinked.
+@cindex relinking
+
+Thus, if we change the file @file{insert.c} and run @code{make},
+@code{make} will compile that file to update @file{insert.o}, and then
+link @file{edit}.  If we change the file @file{command.h} and run
+@code{make}, @code{make} will recompile the object files @file{kbd.o},
+@file{command.o} and @file{files.o} and then link the file @file{edit}.
+
+@node Variables Simplify, make Deduces, How Make Works, Introduction
+@section Variables Make Makefiles Simpler
+@cindex variables
+@cindex simplifying with variables
+
+In our example, we had to list all the object files twice in the rule for
+@file{edit} (repeated here):
+
+@example
+@group
+edit : main.o kbd.o command.o display.o \
+              insert.o search.o files.o utils.o
+        cc -o edit main.o kbd.o command.o display.o \
+                   insert.o search.o files.o utils.o
+@end group
+@end example
+
+@cindex @code{objects}
+Such duplication is error-prone; if a new object file is added to the
+system, we might add it to one list and forget the other.  We can eliminate
+the risk and simplify the makefile by using a variable.  @dfn{Variables}
+allow a text string to be defined once and substituted in multiple places
+later (@pxref{Using Variables, ,How to Use Variables}).
+
+@cindex @code{OBJECTS}
+@cindex @code{objs}
+@cindex @code{OBJS}
+@cindex @code{obj}
+@cindex @code{OBJ}
+It is standard practice for every makefile to have a variable named
+@code{objects}, @code{OBJECTS}, @code{objs}, @code{OBJS}, @code{obj},
+or @code{OBJ} which is a list of all object file names.  We would
+define such a variable @code{objects} with a line like this in the
+makefile:@refill
+
+@example
+@group
+objects = main.o kbd.o command.o display.o \
+          insert.o search.o files.o utils.o
+@end group
+@end example
+
+@noindent
+Then, each place we want to put a list of the object file names, we can
+substitute the variable's value by writing @samp{$(objects)}
+(@pxref{Using Variables, ,How to Use Variables}).
+
+Here is how the complete simple makefile looks when you use a variable
+for the object files:
+
+@example
+@group
+objects = main.o kbd.o command.o display.o \
+          insert.o search.o files.o utils.o
+
+edit : $(objects)
+        cc -o edit $(objects)
+main.o : main.c defs.h
+        cc -c main.c
+kbd.o : kbd.c defs.h command.h
+        cc -c kbd.c
+command.o : command.c defs.h command.h
+        cc -c command.c
+display.o : display.c defs.h buffer.h
+        cc -c display.c
+insert.o : insert.c defs.h buffer.h
+        cc -c insert.c
+search.o : search.c defs.h buffer.h
+        cc -c search.c
+files.o : files.c defs.h buffer.h command.h
+        cc -c files.c
+utils.o : utils.c defs.h
+        cc -c utils.c
+clean :
+        rm edit $(objects)
+@end group
+@end example
+
+@node make Deduces, Combine By Prerequisite, Variables Simplify, Introduction
+@section Letting @code{make} Deduce the Commands
+@cindex deducing commands (implicit rules)
+@cindex implicit rule, introduction to
+@cindex rule, implicit, introduction to
+
+It is not necessary to spell out the commands for compiling the individual
+C source files, because @code{make} can figure them out: it has an
+@dfn{implicit rule} for updating a @samp{.o} file from a correspondingly
+named @samp{.c} file using a @samp{cc -c} command.  For example, it will
+use the command @samp{cc -c main.c -o main.o} to compile @file{main.c} into
+@file{main.o}.  We can therefore omit the commands from the rules for the
+object files.  @xref{Implicit Rules, ,Using Implicit Rules}.@refill
+
+When a @samp{.c} file is used automatically in this way, it is also
+automatically added to the list of prerequisites.  We can therefore omit
+the @samp{.c} files from the prerequisites, provided we omit the commands.
+
+Here is the entire example, with both of these changes, and a variable
+@code{objects} as suggested above:
+
+@example
+@group
+objects = main.o kbd.o command.o display.o \
+          insert.o search.o files.o utils.o
+
+edit : $(objects)
+        cc -o edit $(objects)
+
+main.o : defs.h
+kbd.o : defs.h command.h
+command.o : defs.h command.h
+display.o : defs.h buffer.h
+insert.o : defs.h buffer.h
+search.o : defs.h buffer.h
+files.o : defs.h buffer.h command.h
+utils.o : defs.h
+
+.PHONY : clean
+clean :
+        rm edit $(objects)
+@end group
+@end example
+
+@noindent
+This is how we would write the makefile in actual practice.  (The
+complications associated with @samp{clean} are described elsewhere.
+See @ref{Phony Targets}, and @ref{Errors, ,Errors in Commands}.)
+
+Because implicit rules are so convenient, they are important.  You
+will see them used frequently.@refill
+
+@node Combine By Prerequisite, Cleanup, make Deduces, Introduction
+@section Another Style of Makefile
+@cindex combining rules by prerequisite
+
+When the objects of a makefile are created only by implicit rules, an
+alternative style of makefile is possible.  In this style of makefile,
+you group entries by their prerequisites instead of by their targets.
+Here is what one looks like:
+
+@example
+@group
+objects = main.o kbd.o command.o display.o \
+          insert.o search.o files.o utils.o
+
+edit : $(objects)
+        cc -o edit $(objects)
+
+$(objects) : defs.h
+kbd.o command.o files.o : command.h
+display.o insert.o search.o files.o : buffer.h
+@end group
+@end example
+
+@noindent
+Here @file{defs.h} is given as a prerequisite of all the object files;
+@file{command.h} and @file{buffer.h} are prerequisites of the specific
+object files listed for them.
+
+Whether this is better is a matter of taste: it is more compact, but some
+people dislike it because they find it clearer to put all the information
+about each target in one place.
+
+@node Cleanup,  , Combine By Prerequisite, Introduction
+@section Rules for Cleaning the Directory
+@cindex cleaning up
+@cindex removing, to clean up
+
+Compiling a program is not the only thing you might want to write rules
+for.  Makefiles commonly tell how to do a few other things besides
+compiling a program: for example, how to delete all the object files
+and executables so that the directory is @samp{clean}.
+
+@cindex @code{clean} target
+Here is how we
+could write a @code{make} rule for cleaning our example editor:
+
+@example
+@group
+clean:
+        rm edit $(objects)
+@end group
+@end example
+
+In practice, we might want to write the rule in a somewhat more
+complicated manner to handle unanticipated situations.  We would do this:
+
+@example
+@group
+.PHONY : clean
+clean :
+        -rm edit $(objects)
+@end group
+@end example
+
+@noindent
+This prevents @code{make} from getting confused by an actual file
+called @file{clean} and causes it to continue in spite of errors from
+@code{rm}.  (See @ref{Phony Targets}, and @ref{Errors, ,Errors in
+Commands}.)
+
+@noindent
+A rule such as this should not be placed at the beginning of the
+makefile, because we do not want it to run by default!  Thus, in the
+example makefile, we want the rule for @code{edit}, which recompiles
+the editor, to remain the default goal.
+
+Since @code{clean} is not a prerequisite of @code{edit}, this rule will not
+run at all if we give the command @samp{make} with no arguments.  In
+order to make the rule run, we have to type @samp{make clean}.
+@xref{Running, ,How to Run @code{make}}.
+
+@node Makefiles, Rules, Introduction, Top
+@chapter Writing Makefiles
+
+@cindex makefile, how to write
+The information that tells @code{make} how to recompile a system comes from
+reading a data base called the @dfn{makefile}.
+
+@menu
+* Makefile Contents::           What makefiles contain.
+* Makefile Names::              How to name your makefile.
+* Include::                     How one makefile can use another makefile.
+* MAKEFILES Variable::          The environment can specify extra makefiles.
+* MAKEFILE_LIST Variable::      Discover which makefiles have been read.
+* Remaking Makefiles::          How makefiles get remade.
+* Overriding Makefiles::        How to override part of one makefile
+                                  with another makefile.
+* Reading Makefiles::           How makefiles are parsed.
+@end menu
+
+@node Makefile Contents, Makefile Names, Makefiles, Makefiles
+@section What Makefiles Contain
+
+Makefiles contain five kinds of things: @dfn{explicit rules},
+@dfn{implicit rules}, @dfn{variable definitions}, @dfn{directives},
+and @dfn{comments}.  Rules, variables, and directives are described at
+length in later chapters.@refill
+
+@itemize @bullet
+@cindex rule, explicit, definition of
+@cindex explicit rule, definition of
+@item
+An @dfn{explicit rule} says when and how to remake one or more files,
+called the rule's targets.  It lists the other files that the targets
+depend on, call the @dfn{prerequisites} of the target, and may also give
+commands to use to create or update the targets.  @xref{Rules, ,Writing
+Rules}.
+
+@cindex rule, implicit, definition of
+@cindex implicit rule, definition of
+@item
+An @dfn{implicit rule} says when and how to remake a class of files
+based on their names.  It describes how a target may depend on a file
+with a name similar to the target and gives commands to create or
+update such a target.  @xref{Implicit Rules, ,Using Implicit Rules}.
+
+@cindex variable definition
+@item
+A @dfn{variable definition} is a line that specifies a text string
+value for a variable that can be substituted into the text later.  The
+simple makefile example shows a variable definition for @code{objects}
+as a list of all object files (@pxref{Variables Simplify, , Variables
+Make Makefiles Simpler}).
+
+@cindex directive
+@item
+A @dfn{directive} is a command for @code{make} to do something special while
+reading the makefile.  These include:
+
+@itemize @bullet
+@item
+Reading another makefile (@pxref{Include, ,Including Other Makefiles}).
+
+@item
+Deciding (based on the values of variables) whether to use or
+ignore a part of the makefile (@pxref{Conditionals, ,Conditional Parts of Makefiles}).
+
+@item
+Defining a variable from a verbatim string containing multiple lines
+(@pxref{Defining, ,Defining Variables Verbatim}).
+@end itemize
+
+@cindex comments, in makefile
+@cindex @code{#} (comments), in makefile
+@item
+@samp{#} in a line of a makefile starts a @dfn{comment}.  It and the rest of
+the line are ignored, except that a trailing backslash not escaped by
+another backslash will continue the comment across multiple lines.
+Comments may appear on any of the lines in the makefile, except within a
+@code{define} directive, and perhaps within commands (where the shell
+decides what is a comment).  A line containing just a comment (with
+perhaps spaces before it) is effectively blank, and is ignored.@refill
+@end itemize
+
+@node Makefile Names, Include, Makefile Contents, Makefiles
+@section What Name to Give Your Makefile
+@cindex makefile name
+@cindex name of makefile
+@cindex default makefile name
+@cindex file name of makefile
+
+@c following paragraph rewritten to avoid overfull hbox
+By default, when @code{make} looks for the makefile, it tries the
+following names, in order: @file{GNUmakefile}, @file{makefile}
+and @file{Makefile}.@refill
+@findex Makefile
+@findex GNUmakefile
+@findex makefile
+
+@cindex @code{README}
+Normally you should call your makefile either @file{makefile} or
+@file{Makefile}.  (We recommend @file{Makefile} because it appears
+prominently near the beginning of a directory listing, right near other
+important files such as @file{README}.)  The first name checked,
+@file{GNUmakefile}, is not recommended for most makefiles.  You should
+use this name if you have a makefile that is specific to GNU
+@code{make}, and will not be understood by other versions of
+@code{make}.  Other @code{make} programs look for @file{makefile} and
+@file{Makefile}, but not @file{GNUmakefile}.
+
+If @code{make} finds none of these names, it does not use any makefile.
+Then you must specify a goal with a command argument, and @code{make}
+will attempt to figure out how to remake it using only its built-in
+implicit rules.  @xref{Implicit Rules, ,Using Implicit Rules}.
+
+@cindex @code{-f}
+@cindex @code{--file}
+@cindex @code{--makefile}
+If you want to use a nonstandard name for your makefile, you can specify
+the makefile name with the @samp{-f} or @samp{--file} option.  The
+arguments @w{@samp{-f @var{name}}} or @w{@samp{--file=@var{name}}} tell
+@code{make} to read the file @var{name} as the makefile.  If you use
+more than one @samp{-f} or @samp{--file} option, you can specify several
+makefiles.  All the makefiles are effectively concatenated in the order
+specified.  The default makefile names @file{GNUmakefile},
+@file{makefile} and @file{Makefile} are not checked automatically if you
+specify @samp{-f} or @samp{--file}.@refill
+@cindex specifying makefile name
+@cindex makefile name, how to specify
+@cindex name of makefile, how to specify
+@cindex file name of makefile, how to specify
+
+@node Include, MAKEFILES Variable, Makefile Names, Makefiles
+@section Including Other Makefiles
+@cindex including other makefiles
+@cindex makefile, including
+
+@findex include
+The @code{include} directive tells @code{make} to suspend reading the
+current makefile and read one or more other makefiles before continuing.
+The directive is a line in the makefile that looks like this:
+
+@example
+include @var{filenames}@dots{}
+@end example
+
+@noindent
+@var{filenames} can contain shell file name patterns.
+@cindex shell file name pattern (in @code{include})
+@cindex shell wildcards (in @code{include})
+@cindex wildcard, in @code{include}
+
+Extra spaces are allowed and ignored at the beginning of the line, but
+a tab is not allowed.  (If the line begins with a tab, it will be
+considered a command line.)  Whitespace is required between
+@code{include} and the file names, and between file names; extra
+whitespace is ignored there and at the end of the directive.  A
+comment starting with @samp{#} is allowed at the end of the line.  If
+the file names contain any variable or function references, they are
+expanded.  @xref{Using Variables, ,How to Use Variables}.
+
+For example, if you have three @file{.mk} files, @file{a.mk},
+@file{b.mk}, and @file{c.mk}, and @code{$(bar)} expands to
+@code{bish bash}, then the following expression
+
+@example
+include foo *.mk $(bar)
+@end example
+
+is equivalent to
+
+@example
+include foo a.mk b.mk c.mk bish bash
+@end example
+
+When @code{make} processes an @code{include} directive, it suspends
+reading of the containing makefile and reads from each listed file in
+turn.  When that is finished, @code{make} resumes reading the
+makefile in which the directive appears.
+
+One occasion for using @code{include} directives is when several programs,
+handled by individual makefiles in various directories, need to use a
+common set of variable definitions
+(@pxref{Setting, ,Setting Variables}) or pattern rules
+(@pxref{Pattern Rules, ,Defining and Redefining Pattern Rules}).
+
+Another such occasion is when you want to generate prerequisites from
+source files automatically; the prerequisites can be put in a file that
+is included by the main makefile.  This practice is generally cleaner
+than that of somehow appending the prerequisites to the end of the main
+makefile as has been traditionally done with other versions of
+@code{make}.  @xref{Automatic Prerequisites}.
+@cindex prerequisites, automatic generation
+@cindex automatic generation of prerequisites
+@cindex generating prerequisites automatically
+
+@cindex @code{-I}
+@cindex @code{--include-dir}
+@cindex included makefiles, default directories
+@cindex default directories for included makefiles
+@findex /usr/gnu/include
+@findex /usr/local/include
+@findex /usr/include
+If the specified name does not start with a slash, and the file is not
+found in the current directory, several other directories are searched.
+First, any directories you have specified with the @samp{-I} or
+@samp{--include-dir} option are searched
+(@pxref{Options Summary, ,Summary of Options}).
+Then the following directories (if they exist)
+are searched, in this order:
+@file{@var{prefix}/include} (normally @file{/usr/local/include}
+@footnote{GNU Make compiled for MS-DOS and MS-Windows behaves as if
+@var{prefix} has been defined to be the root of the DJGPP tree
+hierarchy.})
+@file{/usr/gnu/include},
+@file{/usr/local/include}, @file{/usr/include}.
+
+If an included makefile cannot be found in any of these directories, a
+warning message is generated, but it is not an immediately fatal error;
+processing of the makefile containing the @code{include} continues.
+Once it has finished reading makefiles, @code{make} will try to remake
+any that are out of date or don't exist.
+@xref{Remaking Makefiles, ,How Makefiles Are Remade}.
+Only after it has tried to find a way to remake a makefile and failed,
+will @code{make} diagnose the missing makefile as a fatal error.
+
+If you want @code{make} to simply ignore a makefile which does not exist
+and cannot be remade, with no error message, use the @w{@code{-include}}
+directive instead of @code{include}, like this:
+
+@example
+-include @var{filenames}@dots{}
+@end example
+
+This acts like @code{include} in every way except that there is no
+error (not even a warning) if any of the @var{filenames} do not exist.
+For compatibility with some other @code{make} implementations,
+@code{sinclude} is another name for @w{@code{-include}}.
+
+@node MAKEFILES Variable, MAKEFILE_LIST Variable, Include, Makefiles
+@section The Variable @code{MAKEFILES}
+@cindex makefile, and @code{MAKEFILES} variable
+@cindex including (@code{MAKEFILES} variable)
+
+@vindex MAKEFILES
+If the environment variable @code{MAKEFILES} is defined, @code{make}
+considers its value as a list of names (separated by whitespace) of
+additional makefiles to be read before the others.  This works much like
+the @code{include} directive: various directories are searched for those
+files (@pxref{Include, ,Including Other Makefiles}).  In addition, the
+default goal is never taken from one of these makefiles and it is not an
+error if the files listed in @code{MAKEFILES} are not found.@refill
+
+@cindex recursion, and @code{MAKEFILES} variable
+The main use of @code{MAKEFILES} is in communication between recursive
+invocations of @code{make} (@pxref{Recursion, ,Recursive Use of
+@code{make}}).  It usually is not desirable to set the environment
+variable before a top-level invocation of @code{make}, because it is
+usually better not to mess with a makefile from outside.  However, if
+you are running @code{make} without a specific makefile, a makefile in
+@code{MAKEFILES} can do useful things to help the built-in implicit
+rules work better, such as defining search paths (@pxref{Directory Search}).
+
+Some users are tempted to set @code{MAKEFILES} in the environment
+automatically on login, and program makefiles to expect this to be done.
+This is a very bad idea, because such makefiles will fail to work if run by
+anyone else.  It is much better to write explicit @code{include} directives
+in the makefiles.  @xref{Include, , Including Other Makefiles}.
+
+@node MAKEFILE_LIST Variable, Remaking Makefiles, MAKEFILES Variable, Makefiles
+@comment  node-name,  next,  previous,  up
+@section The Variable @code{MAKEFILE_LIST}
+@cindex makefiles, and @code{MAKEFILE_LIST} variable
+@cindex including (@code{MAKEFILE_LIST} variable)
+
+As @code{make} reads various makefiles, including any obtained from the
+@code{MAKEFILES} variable, the command line, the default files, or
+from @code{include} directives, their names will be automatically
+appended to the @code{MAKEFILE_LIST} variable.  They are added right
+before @code{make} begins to parse them.
+
+This means that if the first thing a makefile does is examine the last
+word in this variable, it will be the name of the current makefile.
+Once the current makefile has used @code{include}, however, the last
+word will be the just-included makefile.
+
+If a makefile named @code{Makefile} has this content:
+
+@example
+@group
+name1 := $(word $(words $(MAKEFILE_LIST)),$(MAKEFILE_LIST))
+
+include inc.mk
+
+name2 := $(word $(words $(MAKEFILE_LIST)),$(MAKEFILE_LIST))
+
+all:
+        @@echo name1 = $(name1)
+        @@echo name2 = $(name2)
+@end group
+@end example
+
+@noindent
+then you would expect to see this output:
+
+@example
+@group
+name1 = Makefile
+name2 = inc.mk
+@end group
+@end example
+
+@xref{Text Functions}, for more information on the @code{word} and
+@code{words} functions used above.  @xref{Flavors, The Two Flavors of
+Variables}, for more information on simply-expanded (@code{:=})
+variable definitions.
+
+@node Remaking Makefiles, Overriding Makefiles, MAKEFILE_LIST Variable, Makefiles
+@section How Makefiles Are Remade
+
+@cindex updating makefiles
+@cindex remaking makefiles
+@cindex makefile, remaking of
+Sometimes makefiles can be remade from other files, such as RCS or SCCS
+files.  If a makefile can be remade from other files, you probably want
+@code{make} to get an up-to-date version of the makefile to read in.
+
+To this end, after reading in all makefiles, @code{make} will consider
+each as a goal target and attempt to update it.  If a makefile has a
+rule which says how to update it (found either in that very makefile or
+in another one) or if an implicit rule applies to it (@pxref{Implicit
+Rules, ,Using Implicit Rules}), it will be updated if necessary.  After
+all makefiles have been checked, if any have actually been changed,
+@code{make} starts with a clean slate and reads all the makefiles over
+again.  (It will also attempt to update each of them over again, but
+normally this will not change them again, since they are already up to
+date.)@refill
+
+If you know that one or more of your makefiles cannot be remade and you
+want to keep @code{make} from performing an implicit rule search on
+them, perhaps for efficiency reasons, you can use any normal method of
+preventing implicit rule lookup to do so.  For example, you can write an
+explicit rule with the makefile as the target, and an empty command
+string (@pxref{Empty Commands, ,Using Empty Commands}).
+
+If the makefiles specify a double-colon rule to remake a file with
+commands but no prerequisites, that file will always be remade
+(@pxref{Double-Colon}).  In the case of makefiles, a makefile that has a
+double-colon rule with commands but no prerequisites will be remade every
+time @code{make} is run, and then again after @code{make} starts over
+and reads the makefiles in again.  This would cause an infinite loop:
+@code{make} would constantly remake the makefile, and never do anything
+else.  So, to avoid this, @code{make} will @strong{not} attempt to
+remake makefiles which are specified as targets of a double-colon rule
+with commands but no prerequisites.@refill
+
+If you do not specify any makefiles to be read with @samp{-f} or
+@samp{--file} options, @code{make} will try the default makefile names;
+@pxref{Makefile Names, ,What Name to Give Your Makefile}.  Unlike
+makefiles explicitly requested with @samp{-f} or @samp{--file} options,
+@code{make} is not certain that these makefiles should exist.  However,
+if a default makefile does not exist but can be created by running
+@code{make} rules, you probably want the rules to be run so that the
+makefile can be used.
+
+Therefore, if none of the default makefiles exists, @code{make} will try
+to make each of them in the same order in which they are searched for
+(@pxref{Makefile Names, ,What Name to Give Your Makefile})
+until it succeeds in making one, or it runs out of names to try.  Note
+that it is not an error if @code{make} cannot find or make any makefile;
+a makefile is not always necessary.@refill
+
+When you use the @samp{-t} or @samp{--touch} option
+(@pxref{Instead of Execution, ,Instead of Executing the Commands}),
+you would not want to use an out-of-date makefile to decide which
+targets to touch.  So the @samp{-t} option has no effect on updating
+makefiles; they are really updated even if @samp{-t} is specified.
+Likewise, @samp{-q} (or @samp{--question}) and @samp{-n} (or
+@samp{--just-print}) do not prevent updating of makefiles, because an
+out-of-date makefile would result in the wrong output for other targets.
+Thus, @samp{make -f mfile -n foo} will update @file{mfile}, read it in,
+and then print the commands to update @file{foo} and its prerequisites
+without running them.  The commands printed for @file{foo} will be those
+specified in the updated contents of @file{mfile}.
+
+However, on occasion you might actually wish to prevent updating of even
+the makefiles.  You can do this by specifying the makefiles as goals in
+the command line as well as specifying them as makefiles.  When the
+makefile name is specified explicitly as a goal, the options @samp{-t}
+and so on do apply to them.
+
+Thus, @samp{make -f mfile -n mfile foo} would read the makefile
+@file{mfile}, print the commands needed to update it without actually
+running them, and then print the commands needed to update @file{foo}
+without running them.  The commands for @file{foo} will be those
+specified by the existing contents of @file{mfile}.
+
+@node Overriding Makefiles, Reading Makefiles, Remaking Makefiles, Makefiles
+@section Overriding Part of Another Makefile
+
+@cindex overriding makefiles
+@cindex makefile, overriding
+Sometimes it is useful to have a makefile that is mostly just like
+another makefile.  You can often use the @samp{include} directive to
+include one in the other, and add more targets or variable definitions.
+However, if the two makefiles give different commands for the same
+target, @code{make} will not let you just do this.  But there is another way.
+
+@cindex match-anything rule, used to override
+In the containing makefile (the one that wants to include the other),
+you can use a match-anything pattern rule to say that to remake any
+target that cannot be made from the information in the containing
+makefile, @code{make} should look in another makefile.
+@xref{Pattern Rules}, for more information on pattern rules.
+
+For example, if you have a makefile called @file{Makefile} that says how
+to make the target @samp{foo} (and other targets), you can write a
+makefile called @file{GNUmakefile} that contains:
+
+@example
+foo:
+        frobnicate > foo
+
+%: force
+        @@$(MAKE) -f Makefile $@@
+force: ;
+@end example
+
+If you say @samp{make foo}, @code{make} will find @file{GNUmakefile},
+read it, and see that to make @file{foo}, it needs to run the command
+@samp{frobnicate > foo}.  If you say @samp{make bar}, @code{make} will
+find no way to make @file{bar} in @file{GNUmakefile}, so it will use the
+commands from the pattern rule: @samp{make -f Makefile bar}.  If
+@file{Makefile} provides a rule for updating @file{bar}, @code{make}
+will apply the rule.  And likewise for any other target that
+@file{GNUmakefile} does not say how to make.
+
+The way this works is that the pattern rule has a pattern of just
+@samp{%}, so it matches any target whatever.  The rule specifies a
+prerequisite @file{force}, to guarantee that the commands will be run even
+if the target file already exists.  We give @file{force} target empty
+commands to prevent @code{make} from searching for an implicit rule to
+build it---otherwise it would apply the same match-anything rule to
+@file{force} itself and create a prerequisite loop!
+
+@node Reading Makefiles,  , Overriding Makefiles, Makefiles
+@section How @code{make} Reads a Makefile
+@cindex reading makefiles
+@cindex makefile, parsing
+
+GNU @code{make} does its work in two distinct phases.  During the first
+phase it reads all the makefiles, included makefiles, etc. and
+internalizes all the variables and their values, implicit and explicit
+rules, and constructs a dependency graph of all the targets and their
+prerequisites.  During the second phase, @code{make} uses these internal
+structures to determine what targets will need to be rebuilt and to
+invoke the rules necessary to do so.
+
+It's important to understand this two-phase approach because it has a
+direct impact on how variable and function expansion happens; this is
+often a source of some confusion when writing makefiles.  Here we will
+present a summary of the phases in which expansion happens for different
+constructs within the makefile.  We say that expansion is
+@dfn{immediate} if it happens during the first phase: in this case
+@code{make} will expand any variables or functions in that section of a
+construct as the makefile is parsed.  We say that expansion is
+@dfn{deferred} if expansion is not performed immediately.  Expansion of
+deferred construct is not performed until either the construct appears
+later in an immediate context, or until the second phase.
+
+You may not be familiar with some of these constructs yet.  You can
+reference this section as you become familiar with them, in later
+chapters.
+
+@subheading Variable Assignment
+@cindex +=, expansion
+@cindex =, expansion
+@cindex ?=, expansion
+@cindex +=, expansion
+@cindex define, expansion
+
+Variable definitions are parsed as follows:
+
+@example
+@var{immediate} = @var{deferred}
+@var{immediate} ?= @var{deferred}
+@var{immediate} := @var{immediate}
+@var{immediate} += @var{deferred} or @var{immediate}
+
+define @var{immediate}
+  @var{deferred}
+endef
+@end example
+
+For the append operator, @samp{+=}, the right-hand side is considered
+immediate if the variable was previously set as a simple variable
+(@samp{:=}), and deferred otherwise.
+
+@subheading Conditional Statements
+@cindex ifdef, expansion
+@cindex ifeq, expansion
+@cindex ifndef, expansion
+@cindex ifneq, expansion
+
+All instances of conditional syntax are parsed immediately, in their
+entirety; this includes the @code{ifdef}, @code{ifeq}, @code{ifndef},
+and @code{ifneq} forms.
+
+@subheading Rule Definition
+@cindex target, expansion
+@cindex prerequisite, expansion
+@cindex implicit rule, expansion
+@cindex pattern rule, expansion
+@cindex explicit rule, expansion
+
+A rule is always expanded the same way, regardless of the form:
+
+@example
+@var{immediate} : @var{immediate} ; @var{deferred}
+	@var{deferred}
+@end example
+
+That is, the target and prerequisite sections are expanded immediately,
+and the commands used to construct the target are always deferred.  This
+general rule is true for explicit rules, pattern rules, suffix rules,
+static pattern rules, and simple prerequisite definitions.
+
+@node Rules, Commands, Makefiles, Top
+@chapter Writing Rules
+@cindex writing rules
+@cindex rule, how to write
+@cindex target
+@cindex prerequisite
+
+A @dfn{rule} appears in the makefile and says when and how to remake
+certain files, called the rule's @dfn{targets} (most often only one per rule).
+It lists the other files that are the @dfn{prerequisites} of the target, and
+@dfn{commands} to use to create or update the target.
+
+@cindex default goal
+@cindex goal, default
+The order of rules is not significant, except for determining the
+@dfn{default goal}: the target for @code{make} to consider, if you do
+not otherwise specify one.  The default goal is the target of the first
+rule in the first makefile.  If the first rule has multiple targets,
+only the first target is taken as the default.  There are two
+exceptions: a target starting with a period is not a default unless it
+contains one or more slashes, @samp{/}, as well; and, a target that
+defines a pattern rule has no effect on the default goal.
+(@xref{Pattern Rules, ,Defining and Redefining Pattern Rules}.)
+
+Therefore, we usually write the makefile so that the first rule is the
+one for compiling the entire program or all the programs described by
+the makefile (often with a target called @samp{all}).
+@xref{Goals, ,Arguments to Specify the Goals}.
+
+@menu
+* Rule Example::                An example explained.
+* Rule Syntax::                 General syntax explained.
+* Wildcards::                   Using wildcard characters such as `*'.
+* Directory Search::            Searching other directories for source files.
+* Phony Targets::               Using a target that is not a real file's name.
+* Force Targets::               You can use a target without commands
+                                  or prerequisites to mark other
+                                  targets as phony.
+* Empty Targets::               When only the date matters and the
+                                  files are empty.
+* Special Targets::             Targets with special built-in meanings.
+* Multiple Targets::            When to make use of several targets in a rule.
+* Multiple Rules::              How to use several rules with the same target.
+* Static Pattern::              Static pattern rules apply to multiple targets
+                                  and can vary the prerequisites according to
+                                  the target name.
+* Double-Colon::                How to use a special kind of rule to allow
+                                  several independent rules for one target.
+* Automatic Prerequisites::     How to automatically generate rules giving
+                                  prerequisites from source files themselves.
+@end menu
+
+@ifinfo
+@node Rule Example, Rule Syntax, Rules, Rules
+@section Rule Example
+
+Here is an example of a rule:
+
+@example
+foo.o : foo.c defs.h       # module for twiddling the frobs
+        cc -c -g foo.c
+@end example
+
+Its target is @file{foo.o} and its prerequisites are @file{foo.c} and
+@file{defs.h}.  It has one command, which is @samp{cc -c -g foo.c}.
+The command line starts with a tab to identify it as a command.
+
+This rule says two things:
+
+@itemize @bullet
+@item
+How to decide whether @file{foo.o} is out of date: it is out of date
+if it does not exist, or if either @file{foo.c} or @file{defs.h} is
+more recent than it.
+
+@item
+How to update the file @file{foo.o}: by running @code{cc} as stated.
+The command does not explicitly mention @file{defs.h}, but we presume
+that @file{foo.c} includes it, and that that is why @file{defs.h} was
+added to the prerequisites.
+@end itemize
+@end ifinfo
+
+@node Rule Syntax, Wildcards, Rule Example, Rules
+@section Rule Syntax
+
+@cindex rule syntax
+@cindex syntax of rules
+In general, a rule looks like this:
+
+@example
+@var{targets} : @var{prerequisites}
+        @var{command}
+        @dots{}
+@end example
+
+@noindent
+or like this:
+
+@example
+@var{targets} : @var{prerequisites} ; @var{command}
+        @var{command}
+        @dots{}
+@end example
+
+@cindex targets
+@cindex rule targets
+The @var{targets} are file names, separated by spaces.  Wildcard
+characters may be used (@pxref{Wildcards, ,Using Wildcard Characters
+in File Names}) and a name of the form @file{@var{a}(@var{m})}
+represents member @var{m} in archive file @var{a}
+(@pxref{Archive Members, ,Archive Members as Targets}).
+Usually there is only one
+target per rule, but occasionally there is a reason to have more
+(@pxref{Multiple Targets, , Multiple Targets in a Rule}).@refill
+
+@cindex commands
+@cindex tab character (in commands)
+The @var{command} lines start with a tab character.  The first command may
+appear on the line after the prerequisites, with a tab character, or may
+appear on the same line, with a semicolon.  Either way, the effect is the
+same.  @xref{Commands, ,Writing the Commands in Rules}.
+
+@cindex dollar sign (@code{$}), in rules
+@cindex @code{$}, in rules
+@cindex rule, and @code{$}
+Because dollar signs are used to start variable references, if you really
+want a dollar sign in a rule you must write two of them, @samp{$$}
+(@pxref{Using Variables, ,How to Use Variables}).
+You may split a long line by inserting a backslash
+followed by a newline, but this is not required, as @code{make} places no
+limit on the length of a line in a makefile.
+
+A rule tells @code{make} two things: when the targets are out of date,
+and how to update them when necessary.
+
+@cindex prerequisites
+@cindex rule prerequisites
+The criterion for being out of date is specified in terms of the
+@var{prerequisites}, which consist of file names separated by spaces.
+(Wildcards and archive members (@pxref{Archives}) are allowed here too.)
+A target is out of date if it does not exist or if it is older than any
+of the prerequisites (by comparison of last-modification times).  The
+idea is that the contents of the target file are computed based on
+information in the prerequisites, so if any of the prerequisites changes,
+the contents of the existing target file are no longer necessarily
+valid.
+
+How to update is specified by @var{commands}.  These are lines to be
+executed by the shell (normally @samp{sh}), but with some extra features
+(@pxref{Commands, ,Writing the Commands in Rules}).
+
+@node Wildcards, Directory Search, Rule Syntax, Rules
+@section Using Wildcard Characters in File Names
+@cindex wildcard
+@cindex file name with wildcards
+@cindex globbing (wildcards)
+
+@cindex @code{*} (wildcard character)
+@cindex @code{?} (wildcard character)
+@cindex @code{[@dots{}]} (wildcard characters)
+A single file name can specify many files using @dfn{wildcard characters}.
+The wildcard characters in @code{make} are @samp{*}, @samp{?} and
+@samp{[@dots{}]}, the same as in the Bourne shell.  For example, @file{*.c}
+specifies a list of all the files (in the working directory) whose names
+end in @samp{.c}.@refill
+
+@cindex @code{~} (tilde)
+@cindex tilde (@code{~})
+@cindex home directory
+The character @samp{~} at the beginning of a file name also has special
+significance.  If alone, or followed by a slash, it represents your home
+directory.  For example @file{~/bin} expands to @file{/home/you/bin}.
+If the @samp{~} is followed by a word, the string represents the home
+directory of the user named by that word.  For example @file{~john/bin}
+expands to @file{/home/john/bin}.  On systems which don't have a home
+directory for each user (such as MS-DOS or MS-Windows), this
+functionality can be simulated by setting the environment variable
+@var{HOME}.@refill
+
+Wildcard expansion happens automatically in targets, in prerequisites,
+and in commands (where the shell does the expansion).  In other
+contexts, wildcard expansion happens only if you request it explicitly
+with the @code{wildcard} function.
+
+The special significance of a wildcard character can be turned off by
+preceding it with a backslash.  Thus, @file{foo\*bar} would refer to a
+specific file whose name consists of @samp{foo}, an asterisk, and
+@samp{bar}.@refill
+
+@menu
+* Wildcard Examples::           Several examples
+* Wildcard Pitfall::            Problems to avoid.
+* Wildcard Function::           How to cause wildcard expansion where
+                                  it does not normally take place.
+@end menu
+
+@node Wildcard Examples, Wildcard Pitfall, Wildcards, Wildcards
+@subsection Wildcard Examples
+
+Wildcards can be used in the commands of a rule, where they are expanded
+by the shell.  For example, here is a rule to delete all the object files:
+
+@example
+@group
+clean:
+        rm -f *.o
+@end group
+@end example
+@cindex @code{rm} (shell command)
+
+Wildcards are also useful in the prerequisites of a rule.  With the
+following rule in the makefile, @samp{make print} will print all the
+@samp{.c} files that have changed since the last time you printed them:
+
+@example
+print: *.c
+        lpr -p $?
+        touch print
+@end example
+
+@cindex @code{print} target
+@cindex @code{lpr} (shell command)
+@cindex @code{touch} (shell command)
+@noindent
+This rule uses @file{print} as an empty target file; see @ref{Empty
+Targets, ,Empty Target Files to Record Events}.  (The automatic variable
+@samp{$?} is used to print only those files that have changed; see
+@ref{Automatic, ,Automatic Variables}.)@refill
+
+Wildcard expansion does not happen when you define a variable.  Thus, if
+you write this:
+
+@example
+objects = *.o
+@end example
+
+@noindent
+then the value of the variable @code{objects} is the actual string
+@samp{*.o}.  However, if you use the value of @code{objects} in a target,
+prerequisite or command, wildcard expansion will take place at that time.
+To set @code{objects} to the expansion, instead use:
+
+@example
+objects := $(wildcard *.o)
+@end example
+
+@noindent
+@xref{Wildcard Function}.
+
+@node Wildcard Pitfall, Wildcard Function, Wildcard Examples, Wildcards
+@subsection Pitfalls of Using Wildcards
+@cindex wildcard pitfalls
+@cindex pitfalls of wildcards
+@cindex mistakes with wildcards
+@cindex errors with wildcards
+@cindex problems with wildcards
+
+Now here is an example of a naive way of using wildcard expansion, that
+does not do what you would intend.  Suppose you would like to say that the
+executable file @file{foo} is made from all the object files in the
+directory, and you write this:
+
+@example
+objects = *.o
+
+foo : $(objects)
+        cc -o foo $(CFLAGS) $(objects)
+@end example
+
+@noindent
+The value of @code{objects} is the actual string @samp{*.o}.  Wildcard
+expansion happens in the rule for @file{foo}, so that each @emph{existing}
+@samp{.o} file becomes a prerequisite of @file{foo} and will be recompiled if
+necessary.
+
+But what if you delete all the @samp{.o} files?  When a wildcard matches
+no files, it is left as it is, so then @file{foo} will depend on the
+oddly-named file @file{*.o}.  Since no such file is likely to exist,
+@code{make} will give you an error saying it cannot figure out how to
+make @file{*.o}.  This is not what you want!
+
+Actually it is possible to obtain the desired result with wildcard
+expansion, but you need more sophisticated techniques, including the
+@code{wildcard} function and string substitution.
+@ifinfo
+@xref{Wildcard Function, ,The Function @code{wildcard}}.
+@end ifinfo
+@iftex
+These are described in the following section.
+@end iftex
+
+@cindex wildcards and MS-DOS/MS-Windows backslashes
+@cindex backslashes in pathnames and wildcard expansion
+
+Microsoft operating systems (MS-DOS and MS-Windows) use backslashes to
+separate directories in pathnames, like so:
+
+@example
+  c:\foo\bar\baz.c
+@end example
+
+This is equivalent to the Unix-style @file{c:/foo/bar/baz.c} (the
+@file{c:} part is the so-called drive letter).  When @code{make} runs on
+these systems, it supports backslashes as well as the Unix-style forward
+slashes in pathnames.  However, this support does @emph{not} include the
+wildcard expansion, where backslash is a quote character.  Therefore,
+you @emph{must} use Unix-style slashes in these cases.
+
+
+@node Wildcard Function,  , Wildcard Pitfall, Wildcards
+@subsection The Function @code{wildcard}
+@findex wildcard
+
+Wildcard expansion happens automatically in rules.  But wildcard expansion
+does not normally take place when a variable is set, or inside the
+arguments of a function.  If you want to do wildcard expansion in such
+places, you need to use the @code{wildcard} function, like this:
+
+@example
+$(wildcard @var{pattern}@dots{})
+@end example
+
+@noindent
+This string, used anywhere in a makefile, is replaced by a
+space-separated list of names of existing files that match one of the
+given file name patterns.  If no existing file name matches a pattern,
+then that pattern is omitted from the output of the @code{wildcard}
+function.  Note that this is different from how unmatched wildcards
+behave in rules, where they are used verbatim rather than ignored
+(@pxref{Wildcard Pitfall}).
+
+One use of the @code{wildcard} function is to get a list of all the C source
+files in a directory, like this:
+
+@example
+$(wildcard *.c)
+@end example
+
+We can change the list of C source files into a list of object files by
+replacing the @samp{.c} suffix with @samp{.o} in the result, like this:
+
+@example
+$(patsubst %.c,%.o,$(wildcard *.c))
+@end example
+
+@noindent
+(Here we have used another function, @code{patsubst}.
+@xref{Text Functions, ,Functions for String Substitution and Analysis}.)@refill
+
+Thus, a makefile to compile all C source files in the directory and then
+link them together could be written as follows:
+
+@example
+objects := $(patsubst %.c,%.o,$(wildcard *.c))
+
+foo : $(objects)
+        cc -o foo $(objects)
+@end example
+
+@noindent
+(This takes advantage of the implicit rule for compiling C programs, so
+there is no need to write explicit rules for compiling the files.
+@xref{Flavors, ,The Two Flavors of Variables}, for an explanation of
+@samp{:=}, which is a variant of @samp{=}.)
+
+@node Directory Search, Phony Targets, Wildcards, Rules
+@section Searching Directories for Prerequisites
+@vindex VPATH
+@findex vpath
+@cindex vpath
+@cindex search path for prerequisites (@code{VPATH})
+@cindex directory search (@code{VPATH})
+
+For large systems, it is often desirable to put sources in a separate
+directory from the binaries.  The @dfn{directory search} features of
+@code{make} facilitate this by searching several directories
+automatically to find a prerequisite.  When you redistribute the files
+among directories, you do not need to change the individual rules,
+just the search paths.
+
+@menu
+* General Search::              Specifying a search path that applies
+                                  to every prerequisite.
+* Selective Search::            Specifying a search path
+                                  for a specified class of names.
+* Search Algorithm::            When and how search paths are applied.
+* Commands/Search::             How to write shell commands that work together
+                                  with search paths.
+* Implicit/Search::             How search paths affect implicit rules.
+* Libraries/Search::            Directory search for link libraries.
+@end menu
+
+@node General Search, Selective Search, Directory Search, Directory Search
+@subsection @code{VPATH}: Search Path for All Prerequisites
+@vindex VPATH
+
+The value of the @code{make} variable @code{VPATH} specifies a list of
+directories that @code{make} should search.  Most often, the
+directories are expected to contain prerequisite files that are not in the
+current directory; however, @code{VPATH} specifies a search list that
+@code{make} applies for all files, including files which are targets of
+rules.
+
+Thus, if a file that is listed as a target or prerequisite does not exist
+in the current directory, @code{make} searches the directories listed in
+@code{VPATH} for a file with that name.  If a file is found in one of
+them, that file may become the prerequisite (see below).  Rules may then
+specify the names of files in the prerequisite list as if they all
+existed in the current directory.  @xref{Commands/Search, ,Writing Shell
+Commands with Directory Search}.
+
+In the @code{VPATH} variable, directory names are separated by colons or
+blanks.  The order in which directories are listed is the order followed
+by @code{make} in its search.  (On MS-DOS and MS-Windows, semi-colons
+are used as separators of directory names in @code{VPATH}, since the
+colon can be used in the pathname itself, after the drive letter.)
+
+For example,
+
+@example
+VPATH = src:../headers
+@end example
+
+@noindent
+specifies a path containing two directories, @file{src} and
+@file{../headers}, which @code{make} searches in that order.
+
+With this value of @code{VPATH}, the following rule,
+
+@example
+foo.o : foo.c
+@end example
+
+@noindent
+is interpreted as if it were written like this:
+
+@example
+foo.o : src/foo.c
+@end example
+
+@noindent
+assuming the file @file{foo.c} does not exist in the current directory but
+is found in the directory @file{src}.
+
+@node Selective Search, Search Algorithm, General Search, Directory Search
+@subsection The @code{vpath} Directive
+@findex vpath
+
+Similar to the @code{VPATH} variable, but more selective, is the
+@code{vpath} directive (note lower case), which allows you to specify a
+search path for a particular class of file names: those that match a
+particular pattern.  Thus you can supply certain search directories for
+one class of file names and other directories (or none) for other file
+names.
+
+There are three forms of the @code{vpath} directive:
+
+@table @code
+@item vpath @var{pattern} @var{directories}
+Specify the search path @var{directories} for file names that match
+@var{pattern}.
+
+The search path, @var{directories}, is a list of directories to be
+searched, separated by colons (semi-colons on MS-DOS and MS-Windows) or
+blanks, just like the search path used in the @code{VPATH} variable.
+
+@item vpath @var{pattern}
+Clear out the search path associated with @var{pattern}.
+
+@c Extra blank line makes sure this gets two lines.
+@item vpath
+
+Clear all search paths previously specified with @code{vpath} directives.
+@end table
+
+A @code{vpath} pattern is a string containing a @samp{%} character.  The
+string must match the file name of a prerequisite that is being searched
+for, the @samp{%} character matching any sequence of zero or more
+characters (as in pattern rules; @pxref{Pattern Rules, ,Defining and
+Redefining Pattern Rules}).  For example, @code{%.h} matches files that
+end in @code{.h}.  (If there is no @samp{%}, the pattern must match the
+prerequisite exactly, which is not useful very often.)
+
+@cindex @code{%}, quoting in @code{vpath}
+@cindex @code{%}, quoting with @code{\} (backslash)
+@cindex @code{\} (backslash), to quote @code{%}
+@cindex backslash (@code{\}), to quote @code{%}
+@cindex quoting @code{%}, in @code{vpath}
+@samp{%} characters in a @code{vpath} directive's pattern can be quoted
+with preceding backslashes (@samp{\}).  Backslashes that would otherwise
+quote @samp{%} characters can be quoted with more backslashes.
+Backslashes that quote @samp{%} characters or other backslashes are
+removed from the pattern before it is compared to file names.  Backslashes
+that are not in danger of quoting @samp{%} characters go unmolested.@refill
+
+When a prerequisite fails to exist in the current directory, if the
+@var{pattern} in a @code{vpath} directive matches the name of the
+prerequisite file, then the @var{directories} in that directive are searched
+just like (and before) the directories in the @code{VPATH} variable.
+
+For example,
+
+@example
+vpath %.h ../headers
+@end example
+
+@noindent
+tells @code{make} to look for any prerequisite whose name ends in @file{.h}
+in the directory @file{../headers} if the file is not found in the current
+directory.
+
+If several @code{vpath} patterns match the prerequisite file's name, then
+@code{make} processes each matching @code{vpath} directive one by one,
+searching all the directories mentioned in each directive.  @code{make}
+handles multiple @code{vpath} directives in the order in which they
+appear in the makefile; multiple directives with the same pattern are
+independent of each other.
+
+@need 750
+Thus,
+
+@example
+@group
+vpath %.c foo
+vpath %   blish
+vpath %.c bar
+@end group
+@end example
+
+@noindent
+will look for a file ending in @samp{.c} in @file{foo}, then
+@file{blish}, then @file{bar}, while
+
+@example
+@group
+vpath %.c foo:bar
+vpath %   blish
+@end group
+@end example
+
+@noindent
+will look for a file ending in @samp{.c} in @file{foo}, then
+@file{bar}, then @file{blish}.
+
+@node Search Algorithm, Commands/Search, Selective Search, Directory Search
+@subsection How Directory Searches are Performed
+@cindex algorithm for directory search
+@cindex directory search algorithm
+
+When a prerequisite is found through directory search, regardless of type
+(general or selective), the pathname located may not be the one that
+@code{make} actually provides you in the prerequisite list.  Sometimes
+the path discovered through directory search is thrown away.
+
+The algorithm @code{make} uses to decide whether to keep or abandon a
+path found via directory search is as follows:
+
+@enumerate
+@item
+If a target file does not exist at the path specified in the makefile,
+directory search is performed.
+
+@item
+If the directory search is successful, that path is kept and this file
+is tentatively stored as the target.
+
+@item
+All prerequisites of this target are examined using this same method.
+
+@item
+After processing the prerequisites, the target may or may not need to be
+rebuilt:
+
+@enumerate a
+@item
+If the target does @emph{not} need to be rebuilt, the path to the file
+found during directory search is used for any prerequisite lists which
+contain this target.  In short, if @code{make} doesn't need to rebuild
+the target then you use the path found via directory search.
+
+@item
+If the target @emph{does} need to be rebuilt (is out-of-date), the
+pathname found during directory search is @emph{thrown away}, and the
+target is rebuilt using the file name specified in the makefile.  In
+short, if @code{make} must rebuild, then the target is rebuilt locally,
+not in the directory found via directory search.
+@end enumerate
+@end enumerate
+
+This algorithm may seem complex, but in practice it is quite often
+exactly what you want.
+
+@cindex traditional directory search (GPATH)
+@cindex directory search, traditional (GPATH)
+Other versions of @code{make} use a simpler algorithm: if the file does
+not exist, and it is found via directory search, then that pathname is
+always used whether or not the target needs to be built.  Thus, if the
+target is rebuilt it is created at the pathname discovered during
+directory search.
+
+@vindex GPATH
+If, in fact, this is the behavior you want for some or all of your
+directories, you can use the @code{GPATH} variable to indicate this to
+@code{make}.
+
+@code{GPATH} has the same syntax and format as @code{VPATH} (that is, a
+space- or colon-delimited list of pathnames).  If an out-of-date target
+is found by directory search in a directory that also appears in
+@code{GPATH}, then that pathname is not thrown away.  The target is
+rebuilt using the expanded path.
+
+@node Commands/Search, Implicit/Search, Search Algorithm, Directory Search
+@subsection Writing Shell Commands with Directory Search
+@cindex shell command, and directory search
+@cindex directory search (@code{VPATH}), and shell commands
+
+When a prerequisite is found in another directory through directory search,
+this cannot change the commands of the rule; they will execute as written.
+Therefore, you must write the commands with care so that they will look for
+the prerequisite in the directory where @code{make} finds it.
+
+This is done with the @dfn{automatic variables} such as @samp{$^}
+(@pxref{Automatic, ,Automatic Variables}).
+For instance, the value of @samp{$^} is a
+list of all the prerequisites of the rule, including the names of
+the directories in which they were found, and the value of
+@samp{$@@} is the target.  Thus:@refill
+
+@example
+foo.o : foo.c
+        cc -c $(CFLAGS) $^ -o $@@
+@end example
+
+@noindent
+(The variable @code{CFLAGS} exists so you can specify flags for C
+compilation by implicit rules; we use it here for consistency so it will
+affect all C compilations uniformly;
+@pxref{Implicit Variables, ,Variables Used by Implicit Rules}.)
+
+Often the prerequisites include header files as well, which you do not
+want to mention in the commands.  The automatic variable @samp{$<} is
+just the first prerequisite:
+
+@example
+VPATH = src:../headers
+foo.o : foo.c defs.h hack.h
+        cc -c $(CFLAGS) $< -o $@@
+@end example
+
+@node Implicit/Search, Libraries/Search, Commands/Search, Directory Search
+@subsection Directory Search and Implicit Rules
+@cindex @code{VPATH}, and implicit rules
+@cindex directory search (@code{VPATH}), and implicit rules
+@cindex search path for prerequisites (@code{VPATH}), and implicit rules
+@cindex implicit rule, and directory search
+@cindex implicit rule, and @code{VPATH}
+@cindex rule, implicit, and directory search
+@cindex rule, implicit, and @code{VPATH}
+
+The search through the directories specified in @code{VPATH} or with
+@code{vpath} also happens during consideration of implicit rules
+(@pxref{Implicit Rules, ,Using Implicit Rules}).
+
+For example, when a file @file{foo.o} has no explicit rule, @code{make}
+considers implicit rules, such as the built-in rule to compile
+@file{foo.c} if that file exists.  If such a file is lacking in the
+current directory, the appropriate directories are searched for it.  If
+@file{foo.c} exists (or is mentioned in the makefile) in any of the
+directories, the implicit rule for C compilation is applied.
+
+The commands of implicit rules normally use automatic variables as a
+matter of necessity; consequently they will use the file names found by
+directory search with no extra effort.
+
+@node Libraries/Search,  , Implicit/Search, Directory Search
+@subsection Directory Search for Link Libraries
+@cindex link libraries, and directory search
+@cindex libraries for linking, directory search
+@cindex directory search (@code{VPATH}), and link libraries
+@cindex @code{VPATH}, and link libraries
+@cindex search path for prerequisites (@code{VPATH}), and link libraries
+@cindex @code{-l} (library search)
+@cindex link libraries, patterns matching
+@cindex @code{.LIBPATTERNS}, and link libraries
+@vindex .LIBPATTERNS
+
+Directory search applies in a special way to libraries used with the
+linker.  This special feature comes into play when you write a prerequisite
+whose name is of the form @samp{-l@var{name}}.  (You can tell something
+strange is going on here because the prerequisite is normally the name of a
+file, and the @emph{file name} of a library generally looks like
+@file{lib@var{name}.a}, not like @samp{-l@var{name}}.)@refill
+
+When a prerequisite's name has the form @samp{-l@var{name}}, @code{make}
+handles it specially by searching for the file @file{lib@var{name}.so} in
+the current directory, in directories specified by matching @code{vpath}
+search paths and the @code{VPATH} search path, and then in the
+directories @file{/lib}, @file{/usr/lib}, and @file{@var{prefix}/lib}
+(normally @file{/usr/local/lib}, but MS-DOS/MS-Windows versions of
+@code{make} behave as if @var{prefix} is defined to be the root of the
+DJGPP installation tree).
+
+If that file is not found, then the file @file{lib@var{name}.a} is
+searched for, in the same directories as above.
+
+For example, if there is a @file{/usr/lib/libcurses.a} library on your
+system (and no @file{/usr/lib/libcurses.so} file), then
+
+@example
+@group
+foo : foo.c -lcurses
+        cc $^ -o $@@
+@end group
+@end example
+
+@noindent
+would cause the command @samp{cc foo.c /usr/lib/libcurses.a -o foo} to
+be executed when @file{foo} is older than @file{foo.c} or than
+@file{/usr/lib/libcurses.a}.@refill
+
+Although the default set of files to be searched for is
+@file{lib@var{name}.so} and @file{lib@var{name}.a}, this is customizable
+via the @code{.LIBPATTERNS} variable.  Each word in the value of this
+variable is a pattern string.  When a prerequisite like
+@samp{-l@var{name}} is seen, @code{make} will replace the percent in
+each pattern in the list with @var{name} and perform the above directory
+searches using that library filename.  If no library is found, the next
+word in the list will be used.
+
+The default value for @code{.LIBPATTERNS} is ``@samp{lib%.so lib%.a}'',
+which provides the default behavior described above.
+
+You can turn off link library expansion completely by setting this
+variable to an empty value.
+
+@node Phony Targets, Force Targets, Directory Search, Rules
+@section Phony Targets
+@cindex phony targets
+@cindex targets, phony
+@cindex targets without a file
+
+A phony target is one that is not really the name of a file.  It is just a
+name for some commands to be executed when you make an explicit request.
+There are two reasons to use a phony target: to avoid a conflict with
+a file of the same name, and to improve performance.
+
+If you write a rule whose commands will not create the target file, the
+commands will be executed every time the target comes up for remaking.
+Here is an example:
+
+@example
+@group
+clean:
+        rm *.o temp
+@end group
+@end example
+
+@noindent
+Because the @code{rm} command does not create a file named @file{clean},
+probably no such file will ever exist.  Therefore, the @code{rm} command
+will be executed every time you say @samp{make clean}.
+@cindex @code{rm} (shell command)
+
+@findex .PHONY
+The phony target will cease to work if anything ever does create a file
+named @file{clean} in this directory.  Since it has no prerequisites, the
+file @file{clean} would inevitably be considered up to date, and its
+commands would not be executed.  To avoid this problem, you can explicitly
+declare the target to be phony, using the special target @code{.PHONY}
+(@pxref{Special Targets, ,Special Built-in Target Names}) as follows:
+
+@example
+.PHONY : clean
+@end example
+
+@noindent
+Once this is done, @samp{make clean} will run the commands regardless of
+whether there is a file named @file{clean}.
+
+Since it knows that phony targets do not name actual files that could be
+remade from other files, @code{make} skips the implicit rule search for
+phony targets (@pxref{Implicit Rules}).  This is why declaring a target
+phony is good for performance, even if you are not worried about the
+actual file existing.
+
+Thus, you first write the line that states that @code{clean} is a
+phony target, then you write the rule, like this:
+
+@example
+@group
+.PHONY: clean
+clean:
+        rm *.o temp
+@end group
+@end example
+
+Another example of the usefulness of phony targets is in conjunction
+with recursive invocations of @code{make}.  In this case the makefile
+will often contain a variable which lists a number of subdirectories to
+be built.  One way to handle this is with one rule whose command is a
+shell loop over the subdirectories, like this:
+
+@example
+@group
+SUBDIRS = foo bar baz
+
+subdirs:
+        for dir in $(SUBDIRS); do \
+          $(MAKE) -C $$dir; \
+        done
+@end group
+@end example
+
+There are a few problems with this method, however.  First, any error
+detected in a submake is not noted by this rule, so it will continue to
+build the rest of the directories even when one fails.  This can be
+overcome by adding shell commands to note the error and exit, but then
+it will do so even if @code{make} is invoked with the @code{-k} option,
+which is unfortunate.  Second, and perhaps more importantly, you cannot
+take advantage of the parallel build capabilities of make using this
+method, since there is only one rule.
+
+By declaring the subdirectories as phony targets (you must do this as
+the subdirectory obviously always exists; otherwise it won't be built)
+you can remove these problems:
+
+@example
+@group
+SUBDIRS = foo bar baz
+
+.PHONY: subdirs $(SUBDIRS)
+
+subdirs: $(SUBDIRS)
+
+$(SUBDIRS):
+        $(MAKE) -C $@@
+
+foo: baz
+@end group
+@end example
+
+Here we've also declared that the @file{foo} subdirectory cannot be
+built until after the @file{baz} subdirectory is complete; this kind of
+relationship declaration is particularly important when attempting
+parallel builds.
+
+A phony target should not be a prerequisite of a real target file; if it
+is, its commands are run every time @code{make} goes to update that
+file.  As long as a phony target is never a prerequisite of a real
+target, the phony target commands will be executed only when the phony
+target is a specified goal (@pxref{Goals, ,Arguments to Specify the
+Goals}).
+
+Phony targets can have prerequisites.  When one directory contains multiple
+programs, it is most convenient to describe all of the programs in one
+makefile @file{./Makefile}.  Since the target remade by default will be the
+first one in the makefile, it is common to make this a phony target named
+@samp{all} and give it, as prerequisites, all the individual programs.  For
+example:
+
+@example
+all : prog1 prog2 prog3
+.PHONY : all
+
+prog1 : prog1.o utils.o
+        cc -o prog1 prog1.o utils.o
+
+prog2 : prog2.o
+        cc -o prog2 prog2.o
+
+prog3 : prog3.o sort.o utils.o
+        cc -o prog3 prog3.o sort.o utils.o
+@end example
+
+@noindent
+Now you can say just @samp{make} to remake all three programs, or specify
+as arguments the ones to remake (as in @samp{make prog1 prog3}).
+
+When one phony target is a prerequisite of another, it serves as a subroutine
+of the other.  For example, here @samp{make cleanall} will delete the
+object files, the difference files, and the file @file{program}:
+
+@example
+.PHONY: cleanall cleanobj cleandiff
+
+cleanall : cleanobj cleandiff
+        rm program
+
+cleanobj :
+        rm *.o
+
+cleandiff :
+        rm *.diff
+@end example
+
+@node Force Targets, Empty Targets, Phony Targets, Rules
+@section Rules without Commands or Prerequisites
+@cindex force targets
+@cindex targets, force
+@cindex @code{FORCE}
+@cindex rule, no commands or prerequisites
+
+If a rule has no prerequisites or commands, and the target of the rule
+is a nonexistent file, then @code{make} imagines this target to have
+been updated whenever its rule is run.  This implies that all targets
+depending on this one will always have their commands run.
+
+An example will illustrate this:
+
+@example
+@group
+clean: FORCE
+        rm $(objects)
+FORCE:
+@end group
+@end example
+
+Here the target @samp{FORCE} satisfies the special conditions, so the
+target @file{clean} that depends on it is forced to run its commands.
+There is nothing special about the name @samp{FORCE}, but that is one name
+commonly used this way.
+
+As you can see, using @samp{FORCE} this way has the same results as using
+@samp{.PHONY: clean}.
+
+Using @samp{.PHONY} is more explicit and more efficient.  However,
+other versions of @code{make} do not support @samp{.PHONY}; thus
+@samp{FORCE} appears in many makefiles.  @xref{Phony Targets}.
+
+@node Empty Targets, Special Targets, Force Targets, Rules
+@section Empty Target Files to Record Events
+@cindex empty targets
+@cindex targets, empty
+@cindex recording events with empty targets
+
+The @dfn{empty target} is a variant of the phony target; it is used to hold
+commands for an action that you request explicitly from time to time.
+Unlike a phony target, this target file can really exist; but the file's
+contents do not matter, and usually are empty.
+
+The purpose of the empty target file is to record, with its
+last-modification time, when the rule's commands were last executed.  It
+does so because one of the commands is a @code{touch} command to update the
+target file.
+
+The empty target file should have some prerequisites (otherwise it
+doesn't make sense).  When you ask to remake the empty target, the
+commands are executed if any prerequisite is more recent than the target;
+in other words, if a prerequisite has changed since the last time you
+remade the target.  Here is an example:
+
+@example
+print: foo.c bar.c
+        lpr -p $?
+        touch print
+@end example
+@cindex @code{print} target
+@cindex @code{lpr} (shell command)
+@cindex @code{touch} (shell command)
+
+@noindent
+With this rule, @samp{make print} will execute the @code{lpr} command if
+either source file has changed since the last @samp{make print}.  The
+automatic variable @samp{$?} is used to print only those files that have
+changed (@pxref{Automatic, ,Automatic Variables}).
+
+@node Special Targets, Multiple Targets, Empty Targets, Rules
+@section Special Built-in Target Names
+@cindex special targets
+@cindex built-in special targets
+@cindex targets, built-in special
+
+Certain names have special meanings if they appear as targets.
+
+@table @code
+@findex .PHONY
+@item .PHONY
+
+The prerequisites of the special target @code{.PHONY} are considered to
+be phony targets.  When it is time to consider such a target,
+@code{make} will run its commands unconditionally, regardless of
+whether a file with that name exists or what its last-modification
+time is.  @xref{Phony Targets, ,Phony Targets}.
+
+@findex .SUFFIXES
+@item .SUFFIXES
+
+The prerequisites of the special target @code{.SUFFIXES} are the list
+of suffixes to be used in checking for suffix rules.
+@xref{Suffix Rules, , Old-Fashioned Suffix Rules}.
+
+@findex .DEFAULT
+@item .DEFAULT
+
+The commands specified for @code{.DEFAULT} are used for any target for
+which no rules are found (either explicit rules or implicit rules).
+@xref{Last Resort}.  If @code{.DEFAULT} commands are specified, every
+file mentioned as a prerequisite, but not as a target in a rule, will have
+these commands executed on its behalf.  @xref{Implicit Rule Search,
+,Implicit Rule Search Algorithm}.
+
+@findex .PRECIOUS
+@item .PRECIOUS
+@cindex precious targets
+@cindex preserving with @code{.PRECIOUS}
+
+The targets which @code{.PRECIOUS} depends on are given the following
+special treatment: if @code{make} is killed or interrupted during the
+execution of their commands, the target is not deleted.
+@xref{Interrupts, ,Interrupting or Killing @code{make}}.  Also, if the
+target is an intermediate file, it will not be deleted after it is no
+longer needed, as is normally done.  @xref{Chained Rules, ,Chains of
+Implicit Rules}.  In this latter respect it overlaps with the
+@code{.SECONDARY} special target.
+
+You can also list the target pattern of an implicit rule (such as
+@samp{%.o}) as a prerequisite file of the special target @code{.PRECIOUS}
+to preserve intermediate files created by rules whose target patterns
+match that file's name.
+
+@findex .INTERMEDIATE
+@item .INTERMEDIATE
+@cindex intermediate targets, explicit
+
+The targets which @code{.INTERMEDIATE} depends on are treated as
+intermediate files.  @xref{Chained Rules, ,Chains of Implicit Rules}.
+@code{.INTERMEDIATE} with no prerequisites has no effect.
+
+@findex .SECONDARY
+@item .SECONDARY
+@cindex secondary targets
+@cindex preserving with @code{.SECONDARY}
+
+The targets which @code{.SECONDARY} depends on are treated as
+intermediate files, except that they are never automatically deleted.
+@xref{Chained Rules, ,Chains of Implicit Rules}.
+
+@code{.SECONDARY} with no prerequisites causes all targets to be treated
+as secondary (i.e., no target is removed because it is considered
+intermediate).
+
+@findex .DELETE_ON_ERROR
+@item .DELETE_ON_ERROR
+@cindex removing targets on failure
+
+If @code{.DELETE_ON_ERROR} is mentioned as a target anywhere in the
+makefile, then @code{make} will delete the target of a rule if it has
+changed and its commands exit with a nonzero exit status, just as it
+does when it receives a signal.  @xref{Errors, ,Errors in Commands}.
+
+@findex .IGNORE
+@item .IGNORE
+
+If you specify prerequisites for @code{.IGNORE}, then @code{make} will
+ignore errors in execution of the commands run for those particular
+files.  The commands for @code{.IGNORE} are not meaningful.
+
+If mentioned as a target with no prerequisites, @code{.IGNORE} says to
+ignore errors in execution of commands for all files.  This usage of
+@samp{.IGNORE} is supported only for historical compatibility.  Since
+this affects every command in the makefile, it is not very useful; we
+recommend you use the more selective ways to ignore errors in specific
+commands.  @xref{Errors, ,Errors in Commands}.
+
+@findex .LOW_RESOLUTION_TIME
+@item .LOW_RESOLUTION_TIME
+
+If you specify prerequisites for @code{.LOW_RESOLUTION_TIME},
+@command{make} assumes that these files are created by commands that
+generate low resolution time stamps.  The commands for
+@code{.LOW_RESOLUTION_TIME} are not meaningful.
+
+The high resolution file time stamps of many modern hosts lessen the
+chance of @command{make} incorrectly concluding that a file is up to
+date.  Unfortunately, these hosts provide no way to set a high
+resolution file time stamp, so commands like @samp{cp -p} that
+explicitly set a file's time stamp must discard its subsecond part.  If
+a file is created by such a command, you should list it as a
+prerequisite of @code{.LOW_RESOLUTION_TIME} so that @command{make} does
+not mistakenly conclude that the file is out of date.  For example:
+
+@example
+@group
+.LOW_RESOLUTION_TIME: dst
+dst: src
+        cp -p src dst
+@end group
+@end example
+
+Since @samp{cp -p} discards the subsecond part of @file{src}'s time
+stamp, @file{dst} is typically slightly older than @file{src} even when
+it is up to date.  The @code{.LOW_RESOLUTION_TIME} line causes
+@command{make} to consider @file{dst} to be up to date if its time stamp
+is at the start of the same second that @file{src}'s time stamp is in.
+
+Due to a limitation of the archive format, archive member time stamps
+are always low resolution.  You need not list archive members as
+prerequisites of @code{.LOW_RESOLUTION_TIME}, as @command{make} does this
+automatically.
+
+@findex .SILENT
+@item .SILENT
+
+If you specify prerequisites for @code{.SILENT}, then @code{make} will
+not print the commands to remake those particular files before executing
+them.  The commands for @code{.SILENT} are not meaningful.
+
+If mentioned as a target with no prerequisites, @code{.SILENT} says not
+to print any commands before executing them.  This usage of
+@samp{.SILENT} is supported only for historical compatibility.  We
+recommend you use the more selective ways to silence specific commands.
+@xref{Echoing, ,Command Echoing}.  If you want to silence all commands
+for a particular run of @code{make}, use the @samp{-s} or
+@w{@samp{--silent}} option (@pxref{Options Summary}).
+
+@findex .EXPORT_ALL_VARIABLES
+@item .EXPORT_ALL_VARIABLES
+
+Simply by being mentioned as a target, this tells @code{make} to
+export all variables to child processes by default.
+@xref{Variables/Recursion, ,Communicating Variables to a
+Sub-@code{make}}.
+
+@findex .NOTPARALLEL
+@item .NOTPARALLEL
+@cindex parallel execution, overriding
+
+If @code{.NOTPARALLEL} is mentioned as a target, then this invocation of
+@code{make} will be run serially, even if the @samp{-j} option is
+given.  Any recursively invoked @code{make} command will still be run in
+parallel (unless its makefile contains this target).  Any prerequisites
+on this target are ignored.
+@end table
+
+Any defined implicit rule suffix also counts as a special target if it
+appears as a target, and so does the concatenation of two suffixes, such
+as @samp{.c.o}.  These targets are suffix rules, an obsolete way of
+defining implicit rules (but a way still widely used).  In principle, any
+target name could be special in this way if you break it in two and add
+both pieces to the suffix list.  In practice, suffixes normally begin with
+@samp{.}, so these special target names also begin with @samp{.}.
+@xref{Suffix Rules, ,Old-Fashioned Suffix Rules}.
+
+@node Multiple Targets, Multiple Rules, Special Targets, Rules
+@section Multiple Targets in a Rule
+@cindex multiple targets
+@cindex several targets in a rule
+@cindex targets, multiple
+@cindex rule, with multiple targets
+
+A rule with multiple targets is equivalent to writing many rules, each with
+one target, and all identical aside from that.  The same commands apply to
+all the targets, but their effects may vary because you can substitute the
+actual target name into the command using @samp{$@@}.  The rule contributes
+the same prerequisites to all the targets also.
+
+This is useful in two cases.
+
+@itemize @bullet
+@item
+You want just prerequisites, no commands.  For example:
+
+@example
+kbd.o command.o files.o: command.h
+@end example
+
+@noindent
+gives an additional prerequisite to each of the three object files
+mentioned.
+
+@item
+Similar commands work for all the targets.  The commands do not need
+to be absolutely identical, since the automatic variable @samp{$@@}
+can be used to substitute the particular target to be remade into the
+commands (@pxref{Automatic, ,Automatic Variables}).  For example:
+
+@example
+@group
+bigoutput littleoutput : text.g
+        generate text.g -$(subst output,,$@@) > $@@
+@end group
+@end example
+@findex subst
+
+@noindent
+is equivalent to
+
+@example
+bigoutput : text.g
+        generate text.g -big > bigoutput
+littleoutput : text.g
+        generate text.g -little > littleoutput
+@end example
+
+@noindent
+Here we assume the hypothetical program @code{generate} makes two
+types of output, one if given @samp{-big} and one if given
+@samp{-little}.
+@xref{Text Functions, ,Functions for String Substitution and Analysis},
+for an explanation of the @code{subst} function.
+@end itemize
+
+Suppose you would like to vary the prerequisites according to the target,
+much as the variable @samp{$@@} allows you to vary the commands.
+You cannot do this with multiple targets in an ordinary rule, but you can
+do it with a @dfn{static pattern rule}.
+@xref{Static Pattern, ,Static Pattern Rules}.
+
+@node Multiple Rules, Static Pattern, Multiple Targets, Rules
+@section Multiple Rules for One Target
+@cindex multiple rules for one target
+@cindex several rules for one target
+@cindex rule, multiple for one target
+@cindex target, multiple rules for one
+
+One file can be the target of several rules.  All the prerequisites
+mentioned in all the rules are merged into one list of prerequisites for
+the target.  If the target is older than any prerequisite from any rule,
+the commands are executed.
+
+There can only be one set of commands to be executed for a file.  If
+more than one rule gives commands for the same file, @code{make} uses
+the last set given and prints an error message.  (As a special case,
+if the file's name begins with a dot, no error message is printed.
+This odd behavior is only for compatibility with other implementations
+of @code{make}... you should avoid using it).  Occasionally it is
+useful to have the same target invoke multiple commands which are
+defined in different parts of your makefile; you can use
+@dfn{double-colon rules} (@pxref{Double-Colon}) for this.
+
+An extra rule with just prerequisites can be used to give a few extra
+prerequisites to many files at once.  For example, makefiles often
+have a variable, such as @code{objects}, containing a list of all the
+compiler output files in the system being made.  An easy way to say
+that all of them must be recompiled if @file{config.h} changes is to
+write the following:
+
+@example
+objects = foo.o bar.o
+foo.o : defs.h
+bar.o : defs.h test.h
+$(objects) : config.h
+@end example
+
+This could be inserted or taken out without changing the rules that really
+specify how to make the object files, making it a convenient form to use if
+you wish to add the additional prerequisite intermittently.
+
+Another wrinkle is that the additional prerequisites could be specified with
+a variable that you set with a command argument to @code{make}
+(@pxref{Overriding, ,Overriding Variables}).  For example,
+
+@example
+@group
+extradeps=
+$(objects) : $(extradeps)
+@end group
+@end example
+
+@noindent
+means that the command @samp{make extradeps=foo.h} will consider
+@file{foo.h} as a prerequisite of each object file, but plain @samp{make}
+will not.
+
+If none of the explicit rules for a target has commands, then @code{make}
+searches for an applicable implicit rule to find some commands
+@pxref{Implicit Rules, ,Using Implicit Rules}).
+
+@node Static Pattern, Double-Colon, Multiple Rules, Rules
+@section Static Pattern Rules
+@cindex static pattern rule
+@cindex rule, static pattern
+@cindex pattern rules, static (not implicit)
+@cindex varying prerequisites
+@cindex prerequisites, varying (static pattern)
+
+@dfn{Static pattern rules} are rules which specify multiple targets and
+construct the prerequisite names for each target based on the target name.
+They are more general than ordinary rules with multiple targets because the
+targets do not have to have identical prerequisites.  Their prerequisites must
+be @emph{analogous}, but not necessarily @emph{identical}.
+
+@menu
+* Static Usage::                The syntax of static pattern rules.
+* Static versus Implicit::      When are they better than implicit rules?
+@end menu
+
+@node Static Usage, Static versus Implicit, Static Pattern, Static Pattern
+@subsection Syntax of Static Pattern Rules
+@cindex static pattern rule, syntax of
+@cindex pattern rules, static, syntax of
+
+Here is the syntax of a static pattern rule:
+
+@example
+@var{targets} @dots{}: @var{target-pattern}: @var{prereq-patterns} @dots{}
+        @var{commands}
+        @dots{}
+@end example
+
+@noindent
+The @var{targets} list specifies the targets that the rule applies to.
+The targets can contain wildcard characters, just like the targets of
+ordinary rules (@pxref{Wildcards, ,Using Wildcard Characters in File
+Names}).
+
+@cindex target pattern, static (not implicit)
+@cindex stem
+The @var{target-pattern} and @var{prereq-patterns} say how to compute the
+prerequisites of each target.  Each target is matched against the
+@var{target-pattern} to extract a part of the target name, called the
+@dfn{stem}.  This stem is substituted into each of the @var{prereq-patterns}
+to make the prerequisite names (one from each @var{prereq-pattern}).
+
+Each pattern normally contains the character @samp{%} just once.  When the
+@var{target-pattern} matches a target, the @samp{%} can match any part of
+the target name; this part is called the @dfn{stem}.  The rest of the
+pattern must match exactly.  For example, the target @file{foo.o} matches
+the pattern @samp{%.o}, with @samp{foo} as the stem.  The targets
+@file{foo.c} and @file{foo.out} do not match that pattern.@refill
+
+@cindex prerequisite pattern, static (not implicit)
+The prerequisite names for each target are made by substituting the stem
+for the @samp{%} in each prerequisite pattern.  For example, if one
+prerequisite pattern is @file{%.c}, then substitution of the stem
+@samp{foo} gives the prerequisite name @file{foo.c}.  It is legitimate
+to write a prerequisite pattern that does not contain @samp{%}; then this
+prerequisite is the same for all targets.
+
+@cindex @code{%}, quoting in static pattern
+@cindex @code{%}, quoting with @code{\} (backslash)
+@cindex @code{\} (backslash), to quote @code{%}
+@cindex backslash (@code{\}), to quote @code{%}
+@cindex quoting @code{%}, in static pattern
+@samp{%} characters in pattern rules can be quoted with preceding
+backslashes (@samp{\}).  Backslashes that would otherwise quote @samp{%}
+characters can be quoted with more backslashes.  Backslashes that quote
+@samp{%} characters or other backslashes are removed from the pattern
+before it is compared to file names or has a stem substituted into it.
+Backslashes that are not in danger of quoting @samp{%} characters go
+unmolested.  For example, the pattern @file{the\%weird\\%pattern\\} has
+@samp{the%weird\} preceding the operative @samp{%} character, and
+@samp{pattern\\} following it.  The final two backslashes are left alone
+because they cannot affect any @samp{%} character.@refill
+
+Here is an example, which compiles each of @file{foo.o} and @file{bar.o}
+from the corresponding @file{.c} file:
+
+@example
+@group
+objects = foo.o bar.o
+
+all: $(objects)
+
+$(objects): %.o: %.c
+        $(CC) -c $(CFLAGS) $< -o $@@
+@end group
+@end example
+
+@noindent
+Here @samp{$<} is the automatic variable that holds the name of the
+prerequisite and @samp{$@@} is the automatic variable that holds the name
+of the target; see @ref{Automatic, , Automatic Variables}.
+
+Each target specified must match the target pattern; a warning is issued
+for each target that does not.  If you have a list of files, only some of
+which will match the pattern, you can use the @code{filter} function to
+remove nonmatching file names (@pxref{Text Functions, ,Functions for String Substitution and Analysis}):
+
+@example
+files = foo.elc bar.o lose.o
+
+$(filter %.o,$(files)): %.o: %.c
+        $(CC) -c $(CFLAGS) $< -o $@@
+$(filter %.elc,$(files)): %.elc: %.el
+        emacs -f batch-byte-compile $<
+@end example
+
+@noindent
+In this example the result of @samp{$(filter %.o,$(files))} is
+@file{bar.o lose.o}, and the first static pattern rule causes each of
+these object files to be updated by compiling the corresponding C source
+file.  The result of @w{@samp{$(filter %.elc,$(files))}} is
+@file{foo.elc}, so that file is made from @file{foo.el}.@refill
+
+Another example shows how to use @code{$*} in static pattern rules:
+@vindex $*@r{, and static pattern}
+
+@example
+@group
+bigoutput littleoutput : %output : text.g
+        generate text.g -$* > $@@
+@end group
+@end example
+
+@noindent
+When the @code{generate} command is run, @code{$*} will expand to the
+stem, either @samp{big} or @samp{little}.
+
+@node Static versus Implicit,  , Static Usage, Static Pattern
+@subsection Static Pattern Rules versus Implicit Rules
+@cindex rule, static pattern versus implicit
+@cindex static pattern rule, versus implicit
+
+A static pattern rule has much in common with an implicit rule defined as a
+pattern rule (@pxref{Pattern Rules, ,Defining and Redefining Pattern Rules}).
+Both have a pattern for the target and patterns for constructing the
+names of prerequisites.  The difference is in how @code{make} decides
+@emph{when} the rule applies.
+
+An implicit rule @emph{can} apply to any target that matches its pattern,
+but it @emph{does} apply only when the target has no commands otherwise
+specified, and only when the prerequisites can be found.  If more than one
+implicit rule appears applicable, only one applies; the choice depends on
+the order of rules.
+
+By contrast, a static pattern rule applies to the precise list of targets
+that you specify in the rule.  It cannot apply to any other target and it
+invariably does apply to each of the targets specified.  If two conflicting
+rules apply, and both have commands, that's an error.
+
+The static pattern rule can be better than an implicit rule for these
+reasons:
+
+@itemize @bullet
+@item
+You may wish to override the usual implicit rule for a few
+files whose names cannot be categorized syntactically but
+can be given in an explicit list.
+
+@item
+If you cannot be sure of the precise contents of the directories
+you are using, you may not be sure which other irrelevant files
+might lead @code{make} to use the wrong implicit rule.  The choice
+might depend on the order in which the implicit rule search is done.
+With static pattern rules, there is no uncertainty: each rule applies
+to precisely the targets specified.
+@end itemize
+
+@node Double-Colon, Automatic Prerequisites, Static Pattern, Rules
+@section Double-Colon Rules
+@cindex double-colon rules
+@cindex rule, double-colon (@code{::})
+@cindex multiple rules for one target (@code{::})
+@cindex @code{::} rules (double-colon)
+
+@dfn{Double-colon} rules are rules written with @samp{::} instead of
+@samp{:} after the target names.  They are handled differently from
+ordinary rules when the same target appears in more than one rule.
+
+When a target appears in multiple rules, all the rules must be the same
+type: all ordinary, or all double-colon.  If they are double-colon, each
+of them is independent of the others.  Each double-colon rule's commands
+are executed if the target is older than any prerequisites of that rule.
+If there are no prerequisites for that rule, its commands are always
+executed (even if the target already exists).  This can result in
+executing none, any, or all of the double-colon rules.
+
+Double-colon rules with the same target are in fact completely separate
+from one another.  Each double-colon rule is processed individually, just
+as rules with different targets are processed.
+
+The double-colon rules for a target are executed in the order they appear
+in the makefile.  However, the cases where double-colon rules really make
+sense are those where the order of executing the commands would not matter.
+
+Double-colon rules are somewhat obscure and not often very useful; they
+provide a mechanism for cases in which the method used to update a target
+differs depending on which prerequisite files caused the update, and such
+cases are rare.
+
+Each double-colon rule should specify commands; if it does not, an
+implicit rule will be used if one applies.
+@xref{Implicit Rules, ,Using Implicit Rules}.
+
+@node Automatic Prerequisites,  , Double-Colon, Rules
+@section Generating Prerequisites Automatically
+@cindex prerequisites, automatic generation
+@cindex automatic generation of prerequisites
+@cindex generating prerequisites automatically
+
+In the makefile for a program, many of the rules you need to write often
+say only that some object file depends on some header
+file.  For example, if @file{main.c} uses @file{defs.h} via an
+@code{#include}, you would write:
+
+@example
+main.o: defs.h
+@end example
+
+@noindent
+You need this rule so that @code{make} knows that it must remake
+@file{main.o} whenever @file{defs.h} changes.  You can see that for a
+large program you would have to write dozens of such rules in your
+makefile.  And, you must always be very careful to update the makefile
+every time you add or remove an @code{#include}.
+@cindex @code{#include}
+
+@cindex @code{-M} (to compiler)
+To avoid this hassle, most modern C compilers can write these rules for
+you, by looking at the @code{#include} lines in the source files.
+Usually this is done with the @samp{-M} option to the compiler.
+For example, the command:
+
+@example
+cc -M main.c
+@end example
+
+@noindent
+generates the output:
+
+@example
+main.o : main.c defs.h
+@end example
+
+@noindent
+Thus you no longer have to write all those rules yourself.
+The compiler will do it for you.
+
+Note that such a prerequisite constitutes mentioning @file{main.o} in a
+makefile, so it can never be considered an intermediate file by implicit
+rule search.  This means that @code{make} won't ever remove the file
+after using it; @pxref{Chained Rules, ,Chains of Implicit Rules}.
+
+@cindex @code{make depend}
+With old @code{make} programs, it was traditional practice to use this
+compiler feature to generate prerequisites on demand with a command like
+@samp{make depend}.  That command would create a file @file{depend}
+containing all the automatically-generated prerequisites; then the
+makefile could use @code{include} to read them in (@pxref{Include}).
+
+In GNU @code{make}, the feature of remaking makefiles makes this
+practice obsolete---you need never tell @code{make} explicitly to
+regenerate the prerequisites, because it always regenerates any makefile
+that is out of date.  @xref{Remaking Makefiles}.
+
+The practice we recommend for automatic prerequisite generation is to have
+one makefile corresponding to each source file.  For each source file
+@file{@var{name}.c} there is a makefile @file{@var{name}.d} which lists
+what files the object file @file{@var{name}.o} depends on.  That way
+only the source files that have changed need to be rescanned to produce
+the new prerequisites.
+
+Here is the pattern rule to generate a file of prerequisites (i.e., a makefile)
+called @file{@var{name}.d} from a C source file called @file{@var{name}.c}:
+
+@smallexample
+@group
+%.d: %.c
+        @set -e; rm -f $@@; \
+         $(CC) -M $(CPPFLAGS) $< > $@@.$$$$; \
+         sed 's,\($*\)\.o[ :]*,\1.o $@@ : ,g' < $@@.$$$$ > $@@; \
+         rm -f $@@.$$$$
+@end group
+@end smallexample
+
+@noindent
+@xref{Pattern Rules}, for information on defining pattern rules.  The
+@samp{-e} flag to the shell causes it to exit immediately if the
+@code{$(CC)} command (or any other command) fails (exits with a
+nonzero status).
+@cindex @code{-e} (shell flag)
+
+@cindex @code{-MM} (to GNU compiler)
+With the GNU C compiler, you may wish to use the @samp{-MM} flag instead
+of @samp{-M}.  This omits prerequisites on system header files.
+@xref{Preprocessor Options, , Options Controlling the Preprocessor,
+gcc.info, Using GNU CC}, for details.
+
+@cindex @code{sed} (shell command)
+The purpose of the @code{sed} command is to translate (for example):
+
+@example
+main.o : main.c defs.h
+@end example
+
+@noindent
+into:
+
+@example
+main.o main.d : main.c defs.h
+@end example
+
+@noindent
+@cindex @code{.d}
+This makes each @samp{.d} file depend on all the source and header files
+that the corresponding @samp{.o} file depends on.  @code{make} then
+knows it must regenerate the prerequisites whenever any of the source or
+header files changes.
+
+Once you've defined the rule to remake the @samp{.d} files,
+you then use the @code{include} directive to read them all in.
+@xref{Include}.  For example:
+
+@example
+@group
+sources = foo.c bar.c
+
+include $(sources:.c=.d)
+@end group
+@end example
+
+@noindent
+(This example uses a substitution variable reference to translate the
+list of source files @samp{foo.c bar.c} into a list of prerequisite
+makefiles, @samp{foo.d bar.d}.  @xref{Substitution Refs}, for full
+information on substitution references.)  Since the @samp{.d} files are
+makefiles like any others, @code{make} will remake them as necessary
+with no further work from you.  @xref{Remaking Makefiles}.
+
+Note that the @samp{.d} files contain target definitions; you should
+be sure to place the @code{include} directive @emph{after} the first,
+default target in your makefiles or run the risk of having a random
+object file become the default target.
+@xref{How Make Works}.
+
+@node Commands, Using Variables, Rules, Top
+@chapter Writing the Commands in Rules
+@cindex commands, how to write
+@cindex rule commands
+@cindex writing rule commands
+
+The commands of a rule consist of shell command lines to be executed one
+by one.  Each command line must start with a tab, except that the first
+command line may be attached to the target-and-prerequisites line with a
+semicolon in between.  Blank lines and lines of just comments may appear
+among the command lines; they are ignored.  (But beware, an apparently
+``blank'' line that begins with a tab is @emph{not} blank!  It is an
+empty command; @pxref{Empty Commands}.)
+
+Users use many different shell programs, but commands in makefiles are
+always interpreted by @file{/bin/sh} unless the makefile specifies
+otherwise.  @xref{Execution, ,Command Execution}.
+
+@cindex comments, in commands
+@cindex commands, comments in
+@cindex @code{#} (comments), in commands
+The shell that is in use determines whether comments can be written on
+command lines, and what syntax they use.  When the shell is
+@file{/bin/sh}, a @samp{#} starts a comment that extends to the end of
+the line.  The @samp{#} does not have to be at the beginning of a line.
+Text on a line before a @samp{#} is not part of the comment.
+
+@menu
+* Echoing::                     How to control when commands are echoed.
+* Execution::                   How commands are executed.
+* Parallel::                    How commands can be executed in parallel.
+* Errors::                      What happens after a command execution error.
+* Interrupts::                  What happens when a command is interrupted.
+* Recursion::                   Invoking @code{make} from makefiles.
+* Sequences::                   Defining canned sequences of commands.
+* Empty Commands::              Defining useful, do-nothing commands.
+@end menu
+
+@node Echoing, Execution, Commands, Commands
+@section Command Echoing
+@cindex echoing of commands
+@cindex silent operation
+@cindex @code{@@} (in commands)
+@cindex commands, echoing
+@cindex printing of commands
+
+Normally @code{make} prints each command line before it is executed.
+We call this @dfn{echoing} because it gives the appearance that you
+are typing the commands yourself.
+
+When a line starts with @samp{@@}, the echoing of that line is suppressed.
+The @samp{@@} is discarded before the command is passed to the shell.
+Typically you would use this for a command whose only effect is to print
+something, such as an @code{echo} command to indicate progress through
+the makefile:
+
+@example
+@@echo About to make distribution files
+@end example
+
+@cindex @code{-n}
+@cindex @code{--just-print}
+@cindex @code{--dry-run}
+@cindex @code{--recon}
+When @code{make} is given the flag @samp{-n} or @samp{--just-print}
+it only echoes commands, it won't execute them.  @xref{Options Summary,
+,Summary of Options}.  In this case and only this case, even the
+commands starting with @samp{@@} are printed.  This flag is useful for
+finding out which commands @code{make} thinks are necessary without
+actually doing them.
+
+@cindex @code{-s}
+@cindex @code{--silent}
+@cindex @code{--quiet}
+@findex .SILENT
+The @samp{-s} or @samp{--silent}
+flag to @code{make} prevents all echoing, as if all commands
+started with @samp{@@}.  A rule in the makefile for the special target
+@code{.SILENT} without prerequisites has the same effect
+(@pxref{Special Targets, ,Special Built-in Target Names}).
+@code{.SILENT} is essentially obsolete since @samp{@@} is more flexible.@refill
+
+@node Execution, Parallel, Echoing, Commands
+@section Command Execution
+@cindex commands, execution
+@cindex execution, of commands
+@cindex shell command, execution
+@vindex SHELL @r{(command execution)}
+
+When it is time to execute commands to update a target, they are executed
+by making a new subshell for each line.  (In practice, @code{make} may
+take shortcuts that do not affect the results.)
+
+@cindex @code{cd} (shell command)
+@strong{Please note:} this implies that shell commands such as @code{cd}
+that set variables local to each process will not affect the following
+command lines. @footnote{On MS-DOS, the value of current working
+directory is @strong{global}, so changing it @emph{will} affect the
+following command lines on those systems.}  If you want to use @code{cd}
+to affect the next command, put the two on a single line with a
+semicolon between them.  Then @code{make} will consider them a single
+command and pass them, together, to a shell which will execute them in
+sequence.  For example:
+
+@example
+foo : bar/lose
+        cd bar; gobble lose > ../foo
+@end example
+
+@cindex commands, backslash (@code{\}) in
+@cindex commands, quoting newlines in
+@cindex backslash (@code{\}), in commands
+@cindex @code{\} (backslash), in commands
+@cindex quoting newline, in commands
+@cindex newline, quoting, in commands
+If you would like to split a single shell command into multiple lines of
+text, you must use a backslash at the end of all but the last subline.
+Such a sequence of lines is combined into a single line, by deleting the
+backslash-newline sequences, before passing it to the shell.  Thus, the
+following is equivalent to the preceding example:
+
+@example
+@group
+foo : bar/lose
+        cd bar;  \
+        gobble lose > ../foo
+@end group
+@end example
+
+@vindex SHELL
+The program used as the shell is taken from the variable @code{SHELL}.
+By default, the program @file{/bin/sh} is used.
+
+@vindex COMSPEC
+On MS-DOS, if @code{SHELL} is not set, the value of the variable
+@code{COMSPEC} (which is always set) is used instead.
+
+@cindex @code{SHELL}, MS-DOS specifics
+The processing of lines that set the variable @code{SHELL} in Makefiles
+is different on MS-DOS.  The stock shell, @file{command.com}, is
+ridiculously limited in its functionality and many users of @code{make}
+tend to install a replacement shell.  Therefore, on MS-DOS, @code{make}
+examines the value of @code{SHELL}, and changes its behavior based on
+whether it points to a Unix-style or DOS-style shell.  This allows
+reasonable functionality even if @code{SHELL} points to
+@file{command.com}.
+
+If @code{SHELL} points to a Unix-style shell, @code{make} on MS-DOS
+additionally checks whether that shell can indeed be found; if not, it
+ignores the line that sets @code{SHELL}.  In MS-DOS, GNU @code{make}
+searches for the shell in the following places:
+
+@enumerate
+@item
+In the precise place pointed to by the value of @code{SHELL}.  For
+example, if the makefile specifies @samp{SHELL = /bin/sh}, @code{make}
+will look in the directory @file{/bin} on the current drive.
+
+@item
+In the current directory.
+
+@item
+In each of the directories in the @code{PATH} variable, in order.
+
+@end enumerate
+
+In every directory it examines, @code{make} will first look for the
+specific file (@file{sh} in the example above).  If this is not found,
+it will also look in that directory for that file with one of the known
+extensions which identify executable files.  For example @file{.exe},
+@file{.com}, @file{.bat}, @file{.btm}, @file{.sh}, and some others.
+
+If any of these attempts is successful, the value of @code{SHELL} will
+be set to the full pathname of the shell as found.  However, if none of
+these is found, the value of @code{SHELL} will not be changed, and thus
+the line that sets it will be effectively ignored.  This is so
+@code{make} will only support features specific to a Unix-style shell if
+such a shell is actually installed on the system where @code{make} runs.
+
+Note that this extended search for the shell is limited to the cases
+where @code{SHELL} is set from the Makefile; if it is set in the
+environment or command line, you are expected to set it to the full
+pathname of the shell, exactly as things are on Unix.
+
+The effect of the above DOS-specific processing is that a Makefile that
+says @samp{SHELL = /bin/sh} (as many Unix makefiles do), will work
+on MS-DOS unaltered if you have e.g. @file{sh.exe} installed in some
+directory along your @code{PATH}.
+
+@cindex environment, @code{SHELL} in
+Unlike most variables, the variable @code{SHELL} is never set from the
+environment.  This is because the @code{SHELL} environment variable is
+used to specify your personal choice of shell program for interactive
+use.  It would be very bad for personal choices like this to affect the
+functioning of makefiles.  @xref{Environment, ,Variables from the
+Environment}.  However, on MS-DOS and MS-Windows the value of
+@code{SHELL} in the environment @strong{is} used, since on those systems
+most users do not set this variable, and therefore it is most likely set
+specifically to be used by @code{make}.  On MS-DOS, if the setting of
+@code{SHELL} is not suitable for @code{make}, you can set the variable
+@code{MAKESHELL} to the shell that @code{make} should use; this will
+override the value of @code{SHELL}.
+
+@node Parallel, Errors, Execution, Commands
+@section Parallel Execution
+@cindex commands, execution in parallel
+@cindex parallel execution
+@cindex execution, in parallel
+@cindex job slots
+@cindex @code{-j}
+@cindex @code{--jobs}
+
+GNU @code{make} knows how to execute several commands at once.
+Normally, @code{make} will execute only one command at a time, waiting
+for it to finish before executing the next.  However, the @samp{-j} or
+@samp{--jobs} option tells @code{make} to execute many commands
+simultaneously.@refill
+
+On MS-DOS, the @samp{-j} option has no effect, since that system doesn't
+support multi-processing.
+
+If the @samp{-j} option is followed by an integer, this is the number of
+commands to execute at once; this is called the number of @dfn{job slots}.
+If there is nothing looking like an integer after the @samp{-j} option,
+there is no limit on the number of job slots.  The default number of job
+slots is one, which means serial execution (one thing at a time).
+
+One unpleasant consequence of running several commands simultaneously is
+that output generated by the commands appears whenever each command
+sends it, so messages from different commands may be interspersed.
+
+Another problem is that two processes cannot both take input from the
+same device; so to make sure that only one command tries to take input
+from the terminal at once, @code{make} will invalidate the standard
+input streams of all but one running command.  This means that
+attempting to read from standard input will usually be a fatal error (a
+@samp{Broken pipe} signal) for most child processes if there are
+several.
+@cindex broken pipe
+@cindex standard input
+
+It is unpredictable which command will have a valid standard input stream
+(which will come from the terminal, or wherever you redirect the standard
+input of @code{make}).  The first command run will always get it first, and
+the first command started after that one finishes will get it next, and so
+on.
+
+We will change how this aspect of @code{make} works if we find a better
+alternative.  In the mean time, you should not rely on any command using
+standard input at all if you are using the parallel execution feature; but
+if you are not using this feature, then standard input works normally in
+all commands.
+
+Finally, handling recursive @code{make} invocations raises issues.  For
+more information on this, see
+@ref{Options/Recursion, ,Communicating Options to a Sub-@code{make}}.
+
+If a command fails (is killed by a signal or exits with a nonzero
+status), and errors are not ignored for that command
+(@pxref{Errors, ,Errors in Commands}),
+the remaining command lines to remake the same target will not be run.
+If a command fails and the @samp{-k} or @samp{--keep-going}
+option was not given
+(@pxref{Options Summary, ,Summary of Options}),
+@code{make} aborts execution.  If make
+terminates for any reason (including a signal) with child processes
+running, it waits for them to finish before actually exiting.@refill
+
+@cindex load average
+@cindex limiting jobs based on load
+@cindex jobs, limiting based on load
+@cindex @code{-l} (load average)
+@cindex @code{--max-load}
+@cindex @code{--load-average}
+When the system is heavily loaded, you will probably want to run fewer jobs
+than when it is lightly loaded.  You can use the @samp{-l} option to tell
+@code{make} to limit the number of jobs to run at once, based on the load
+average.  The @samp{-l} or @samp{--max-load}
+option is followed by a floating-point number.  For
+example,
+
+@example
+-l 2.5
+@end example
+
+@noindent
+will not let @code{make} start more than one job if the load average is
+above 2.5.  The @samp{-l} option with no following number removes the
+load limit, if one was given with a previous @samp{-l} option.@refill
+
+More precisely, when @code{make} goes to start up a job, and it already has
+at least one job running, it checks the current load average; if it is not
+lower than the limit given with @samp{-l}, @code{make} waits until the load
+average goes below that limit, or until all the other jobs finish.
+
+By default, there is no load limit.
+
+@node Errors, Interrupts, Parallel, Commands
+@section Errors in Commands
+@cindex errors (in commands)
+@cindex commands, errors in
+@cindex exit status (errors)
+
+After each shell command returns, @code{make} looks at its exit status.
+If the command completed successfully, the next command line is executed
+in a new shell; after the last command line is finished, the rule is
+finished.
+
+If there is an error (the exit status is nonzero), @code{make} gives up on
+the current rule, and perhaps on all rules.
+
+Sometimes the failure of a certain command does not indicate a problem.
+For example, you may use the @code{mkdir} command to ensure that a
+directory exists.  If the directory already exists, @code{mkdir} will
+report an error, but you probably want @code{make} to continue regardless.
+
+@cindex @code{-} (in commands)
+To ignore errors in a command line, write a @samp{-} at the beginning of
+the line's text (after the initial tab).  The @samp{-} is discarded before
+the command is passed to the shell for execution.
+
+For example,
+
+@example
+@group
+clean:
+        -rm -f *.o
+@end group
+@end example
+@cindex @code{rm} (shell command)
+
+@noindent
+This causes @code{rm} to continue even if it is unable to remove a file.
+
+@cindex @code{-i}
+@cindex @code{--ignore-errors}
+@findex .IGNORE
+When you run @code{make} with the @samp{-i} or @samp{--ignore-errors}
+flag, errors are ignored in all commands of all rules.  A rule in the
+makefile for the special target @code{.IGNORE} has the same effect, if
+there are no prerequisites.  These ways of ignoring errors are obsolete
+because @samp{-} is more flexible.
+
+When errors are to be ignored, because of either a @samp{-} or the
+@samp{-i} flag, @code{make} treats an error return just like success,
+except that it prints out a message that tells you the status code
+the command exited with, and says that the error has been ignored.
+
+When an error happens that @code{make} has not been told to ignore,
+it implies that the current target cannot be correctly remade, and neither
+can any other that depends on it either directly or indirectly.  No further
+commands will be executed for these targets, since their preconditions
+have not been achieved.
+
+
+@cindex @code{-k}
+@cindex @code{--keep-going}
+Normally @code{make} gives up immediately in this circumstance, returning a
+nonzero status.  However, if the @samp{-k} or @samp{--keep-going}
+flag is specified, @code{make}
+continues to consider the other prerequisites of the pending targets,
+remaking them if necessary, before it gives up and returns nonzero status.
+For example, after an error in compiling one object file, @samp{make -k}
+will continue compiling other object files even though it already knows
+that linking them will be impossible.  @xref{Options Summary, ,Summary of Options}.
+
+The usual behavior assumes that your purpose is to get the specified
+targets up to date; once @code{make} learns that this is impossible, it
+might as well report the failure immediately.  The @samp{-k} option says
+that the real purpose is to test as many of the changes made in the
+program as possible, perhaps to find several independent problems so
+that you can correct them all before the next attempt to compile.  This
+is why Emacs' @code{compile} command passes the @samp{-k} flag by
+default.
+@cindex Emacs (@code{M-x compile})
+
+@findex .DELETE_ON_ERROR
+@cindex deletion of target files
+@cindex removal of target files
+@cindex target, deleting on error
+Usually when a command fails, if it has changed the target file at all,
+the file is corrupted and cannot be used---or at least it is not
+completely updated.  Yet the file's time stamp says that it is now up to
+date, so the next time @code{make} runs, it will not try to update that
+file.  The situation is just the same as when the command is killed by a
+signal; @pxref{Interrupts}.  So generally the right thing to do is to
+delete the target file if the command fails after beginning to change
+the file.  @code{make} will do this if @code{.DELETE_ON_ERROR} appears
+as a target.  This is almost always what you want @code{make} to do, but
+it is not historical practice; so for compatibility, you must explicitly
+request it.
+
+@node Interrupts, Recursion, Errors, Commands
+@section Interrupting or Killing @code{make}
+@cindex interrupt
+@cindex signal
+@cindex deletion of target files
+@cindex removal of target files
+@cindex target, deleting on interrupt
+@cindex killing (interruption)
+
+If @code{make} gets a fatal signal while a command is executing, it may
+delete the target file that the command was supposed to update.  This is
+done if the target file's last-modification time has changed since
+@code{make} first checked it.
+
+The purpose of deleting the target is to make sure that it is remade from
+scratch when @code{make} is next run.  Why is this?  Suppose you type
+@kbd{Ctrl-c} while a compiler is running, and it has begun to write an
+object file @file{foo.o}.  The @kbd{Ctrl-c} kills the compiler, resulting
+in an incomplete file whose last-modification time is newer than the source
+file @file{foo.c}.  But @code{make} also receives the @kbd{Ctrl-c} signal
+and deletes this incomplete file.  If @code{make} did not do this, the next
+invocation of @code{make} would think that @file{foo.o} did not require
+updating---resulting in a strange error message from the linker when it
+tries to link an object file half of which is missing.
+
+@findex .PRECIOUS
+You can prevent the deletion of a target file in this way by making the
+special target @code{.PRECIOUS} depend on it.  Before remaking a target,
+@code{make} checks to see whether it appears on the prerequisites of
+@code{.PRECIOUS}, and thereby decides whether the target should be deleted
+if a signal happens.  Some reasons why you might do this are that the
+target is updated in some atomic fashion, or exists only to record a
+modification-time (its contents do not matter), or must exist at all
+times to prevent other sorts of trouble.
+
+@node Recursion, Sequences, Interrupts, Commands
+@section Recursive Use of @code{make}
+@cindex recursion
+@cindex subdirectories, recursion for
+
+Recursive use of @code{make} means using @code{make} as a command in a
+makefile.  This technique is useful when you want separate makefiles for
+various subsystems that compose a larger system.  For example, suppose you
+have a subdirectory @file{subdir} which has its own makefile, and you would
+like the containing directory's makefile to run @code{make} on the
+subdirectory.  You can do it by writing this:
+
+@example
+subsystem:
+        cd subdir && $(MAKE)
+@end example
+
+@noindent
+or, equivalently, this (@pxref{Options Summary, ,Summary of Options}):
+
+@example
+subsystem:
+        $(MAKE) -C subdir
+@end example
+@cindex @code{-C}
+@cindex @code{--directory}
+
+You can write recursive @code{make} commands just by copying this example,
+but there are many things to know about how they work and why, and about
+how the sub-@code{make} relates to the top-level @code{make}.
+
+For your convenience, GNU @code{make} sets the variable @code{CURDIR} to
+the pathname of the current working directory for you.  If @code{-C} is
+in effect, it will contain the path of the new directory, not the
+original.  The value has the same precedence it would have if it were
+set in the makefile (by default, an environment variable @code{CURDIR}
+will not override this value).  Note that setting this variable has no
+effect on the operation of @code{make}
+
+@menu
+* MAKE Variable::               The special effects of using @samp{$(MAKE)}.
+* Variables/Recursion::         How to communicate variables to a sub-@code{make}.
+* Options/Recursion::           How to communicate options to a sub-@code{make}.
+* -w Option::                   How the @samp{-w} or @samp{--print-directory} option
+                                  helps debug use of recursive @code{make} commands.
+@end menu
+
+@node MAKE Variable, Variables/Recursion, Recursion, Recursion
+@subsection How the @code{MAKE} Variable Works
+@vindex MAKE
+@cindex recursion, and @code{MAKE} variable
+
+Recursive @code{make} commands should always use the variable @code{MAKE},
+not the explicit command name @samp{make}, as shown here:
+
+@example
+@group
+subsystem:
+        cd subdir && $(MAKE)
+@end group
+@end example
+
+The value of this variable is the file name with which @code{make} was
+invoked.  If this file name was @file{/bin/make}, then the command executed
+is @samp{cd subdir && /bin/make}.  If you use a special version of
+@code{make} to run the top-level makefile, the same special version will be
+executed for recursive invocations.
+@cindex @code{cd} (shell command)
+
+As a special feature, using the variable @code{MAKE} in the commands of
+a rule alters the effects of the @samp{-t} (@samp{--touch}), @samp{-n}
+(@samp{--just-print}), or @samp{-q} (@w{@samp{--question}}) option.
+Using the @code{MAKE} variable has the same effect as using a @samp{+}
+character at the beginning of the command line.  @xref{Instead of
+Execution, ,Instead of Executing the Commands}.@refill
+
+Consider the command @samp{make -t} in the above example.  (The
+@samp{-t} option marks targets as up to date without actually running
+any commands; see @ref{Instead of Execution}.)  Following the usual
+definition of @samp{-t}, a @samp{make -t} command in the example would
+create a file named @file{subsystem} and do nothing else.  What you
+really want it to do is run @samp{@w{cd subdir &&} @w{make -t}}; but that would
+require executing the command, and @samp{-t} says not to execute
+commands.@refill
+@cindex @code{-t}, and recursion
+@cindex recursion, and @code{-t}
+@cindex @code{--touch}, and recursion
+
+The special feature makes this do what you want: whenever a command
+line of a rule contains the variable @code{MAKE}, the flags @samp{-t},
+@samp{-n} and @samp{-q} do not apply to that line.  Command lines
+containing @code{MAKE} are executed normally despite the presence of a
+flag that causes most commands not to be run.  The usual
+@code{MAKEFLAGS} mechanism passes the flags to the sub-@code{make}
+(@pxref{Options/Recursion, ,Communicating Options to a
+Sub-@code{make}}), so your request to touch the files, or print the
+commands, is propagated to the subsystem.@refill
+
+@node Variables/Recursion, Options/Recursion, MAKE Variable, Recursion
+@subsection Communicating Variables to a Sub-@code{make}
+@cindex sub-@code{make}
+@cindex environment, and recursion
+@cindex exporting variables
+@cindex variables, environment
+@cindex variables, exporting
+@cindex recursion, and environment
+@cindex recursion, and variables
+
+Variable values of the top-level @code{make} can be passed to the
+sub-@code{make} through the environment by explicit request.  These
+variables are defined in the sub-@code{make} as defaults, but do not
+override what is specified in the makefile used by the sub-@code{make}
+makefile unless you use the @samp{-e} switch (@pxref{Options Summary,
+,Summary of Options}).@refill
+
+To pass down, or @dfn{export}, a variable, @code{make} adds the variable
+and its value to the environment for running each command.  The
+sub-@code{make}, in turn, uses the environment to initialize its table
+of variable values.  @xref{Environment, ,Variables from the
+Environment}.
+
+Except by explicit request, @code{make} exports a variable only if it
+is either defined in the environment initially or set on the command
+line, and if its name consists only of letters, numbers, and underscores.
+Some shells cannot cope with environment variable names consisting of
+characters other than letters, numbers, and underscores.
+
+The special variables @code{SHELL} and @code{MAKEFLAGS} are always
+exported (unless you unexport them).
+@code{MAKEFILES} is exported if you set it to anything.
+
+@code{make} automatically passes down variable values that were defined
+on the command line, by putting them in the @code{MAKEFLAGS} variable.
+@iftex
+See the next section.
+@end iftex
+@ifinfo
+@xref{Options/Recursion}.
+@end ifinfo
+
+Variables are @emph{not} normally passed down if they were created by
+default by @code{make} (@pxref{Implicit Variables, ,Variables Used by
+Implicit Rules}).  The sub-@code{make} will define these for
+itself.@refill
+
+@findex export
+If you want to export specific variables to a sub-@code{make}, use the
+@code{export} directive, like this:
+
+@example
+export @var{variable} @dots{}
+@end example
+
+@noindent
+@findex unexport
+If you want to @emph{prevent} a variable from being exported, use the
+@code{unexport} directive, like this:
+
+@example
+unexport @var{variable} @dots{}
+@end example
+
+@noindent
+As a convenience, you can define a variable and export it at the same
+time by doing:
+
+@example
+export @var{variable} = value
+@end example
+
+@noindent
+has the same result as:
+
+@example
+@var{variable} = value
+export @var{variable}
+@end example
+
+@noindent
+and
+
+@example
+export @var{variable} := value
+@end example
+
+@noindent
+has the same result as:
+
+@example
+@var{variable} := value
+export @var{variable}
+@end example
+
+Likewise,
+
+@example
+export @var{variable} += value
+@end example
+
+@noindent
+is just like:
+
+@example
+@var{variable} += value
+export @var{variable}
+@end example
+
+@noindent
+@xref{Appending, ,Appending More Text to Variables}.
+
+You may notice that the @code{export} and @code{unexport} directives
+work in @code{make} in the same way they work in the shell, @code{sh}.
+
+If you want all variables to be exported by default, you can use
+@code{export} by itself:
+
+@example
+export
+@end example
+
+@noindent
+This tells @code{make} that variables which are not explicitly mentioned
+in an @code{export} or @code{unexport} directive should be exported.
+Any variable given in an @code{unexport} directive will still @emph{not}
+be exported.  If you use @code{export} by itself to export variables by
+default, variables whose names contain characters other than
+alphanumerics and underscores will not be exported unless specifically
+mentioned in an @code{export} directive.@refill
+
+@findex .EXPORT_ALL_VARIABLES
+The behavior elicited by an @code{export} directive by itself was the
+default in older versions of GNU @code{make}.  If your makefiles depend
+on this behavior and you want to be compatible with old versions of
+@code{make}, you can write a rule for the special target
+@code{.EXPORT_ALL_VARIABLES} instead of using the @code{export} directive.
+This will be ignored by old @code{make}s, while the @code{export}
+directive will cause a syntax error.@refill
+@cindex compatibility in exporting
+
+Likewise, you can use @code{unexport} by itself to tell @code{make}
+@emph{not} to export variables by default.  Since this is the default
+behavior, you would only need to do this if @code{export} had been used
+by itself earlier (in an included makefile, perhaps).  You
+@strong{cannot} use @code{export} and @code{unexport} by themselves to
+have variables exported for some commands and not for others.  The last
+@code{export} or @code{unexport} directive that appears by itself
+determines the behavior for the entire run of @code{make}.@refill
+
+@vindex MAKELEVEL
+@cindex recursion, level of
+As a special feature, the variable @code{MAKELEVEL} is changed when it
+is passed down from level to level.  This variable's value is a string
+which is the depth of the level as a decimal number.  The value is
+@samp{0} for the top-level @code{make}; @samp{1} for a sub-@code{make},
+@samp{2} for a sub-sub-@code{make}, and so on.  The incrementation
+happens when @code{make} sets up the environment for a command.@refill
+
+The main use of @code{MAKELEVEL} is to test it in a conditional
+directive (@pxref{Conditionals, ,Conditional Parts of Makefiles}); this
+way you can write a makefile that behaves one way if run recursively and
+another way if run directly by you.@refill
+
+@vindex MAKEFILES
+You can use the variable @code{MAKEFILES} to cause all sub-@code{make}
+commands to use additional makefiles.  The value of @code{MAKEFILES} is
+a whitespace-separated list of file names.  This variable, if defined in
+the outer-level makefile, is passed down through the environment; then
+it serves as a list of extra makefiles for the sub-@code{make} to read
+before the usual or specified ones.  @xref{MAKEFILES Variable, ,The
+Variable @code{MAKEFILES}}.@refill
+
+@node Options/Recursion, -w Option, Variables/Recursion, Recursion
+@subsection Communicating Options to a Sub-@code{make}
+@cindex options, and recursion
+@cindex recursion, and options
+
+@vindex MAKEFLAGS
+Flags such as @samp{-s} and @samp{-k} are passed automatically to the
+sub-@code{make} through the variable @code{MAKEFLAGS}.  This variable is
+set up automatically by @code{make} to contain the flag letters that
+@code{make} received.  Thus, if you do @w{@samp{make -ks}} then
+@code{MAKEFLAGS} gets the value @samp{ks}.@refill
+
+As a consequence, every sub-@code{make} gets a value for @code{MAKEFLAGS}
+in its environment.  In response, it takes the flags from that value and
+processes them as if they had been given as arguments.
+@xref{Options Summary, ,Summary of Options}.
+
+@cindex command line variable definitions, and recursion
+@cindex variables, command line, and recursion
+@cindex recursion, and command line variable definitions
+Likewise variables defined on the command line are passed to the
+sub-@code{make} through @code{MAKEFLAGS}.  Words in the value of
+@code{MAKEFLAGS} that contain @samp{=}, @code{make} treats as variable
+definitions just as if they appeared on the command line.
+@xref{Overriding, ,Overriding Variables}.
+
+@cindex @code{-C}, and recursion
+@cindex @code{-f}, and recursion
+@cindex @code{-o}, and recursion
+@cindex @code{-W}, and recursion
+@cindex @code{--directory}, and recursion
+@cindex @code{--file}, and recursion
+@cindex @code{--old-file}, and recursion
+@cindex @code{--assume-old}, and recursion
+@cindex @code{--assume-new}, and recursion
+@cindex @code{--new-file}, and recursion
+@cindex recursion, and @code{-C}
+@cindex recursion, and @code{-f}
+@cindex recursion, and @code{-o}
+@cindex recursion, and @code{-W}
+The options @samp{-C}, @samp{-f}, @samp{-o}, and @samp{-W} are not put
+into @code{MAKEFLAGS}; these options are not passed down.@refill
+
+@cindex @code{-j}, and recursion
+@cindex @code{--jobs}, and recursion
+@cindex recursion, and @code{-j}
+@cindex job slots, and recursion
+The @samp{-j} option is a special case (@pxref{Parallel, ,Parallel Execution}).
+If you set it to some numeric value @samp{N} and your operating system
+supports it (most any UNIX system will; others typically won't), the
+parent @code{make} and all the sub-@code{make}s will communicate to
+ensure that there are only @samp{N} jobs running at the same time
+between them all.  Note that any job that is marked recursive
+(@pxref{Instead of Execution, ,Instead of Executing the Commands})
+doesn't count against the total jobs (otherwise we could get @samp{N}
+sub-@code{make}s running and have no slots left over for any real work!)
+
+If your operating system doesn't support the above communication, then
+@samp{-j 1} is always put into @code{MAKEFLAGS} instead of the value you
+specified.  This is because if the @w{@samp{-j}} option were passed down
+to sub-@code{make}s, you would get many more jobs running in parallel
+than you asked for.  If you give @samp{-j} with no numeric argument,
+meaning to run as many jobs as possible in parallel, this is passed
+down, since multiple infinities are no more than one.@refill
+
+If you do not want to pass the other flags down, you must change the
+value of @code{MAKEFLAGS}, like this:
+
+@example
+subsystem:
+        cd subdir && $(MAKE) MAKEFLAGS=
+@end example
+
+@vindex MAKEOVERRIDES
+The command line variable definitions really appear in the variable
+@code{MAKEOVERRIDES}, and @code{MAKEFLAGS} contains a reference to this
+variable.  If you do want to pass flags down normally, but don't want to
+pass down the command line variable definitions, you can reset
+@code{MAKEOVERRIDES} to empty, like this:
+
+@example
+MAKEOVERRIDES =
+@end example
+
+@noindent
+@cindex Arg list too long
+@cindex E2BIG
+This is not usually useful to do.  However, some systems have a small
+fixed limit on the size of the environment, and putting so much
+information into the value of @code{MAKEFLAGS} can exceed it.  If you
+see the error message @samp{Arg list too long}, this may be the problem.
+@findex .POSIX
+@cindex POSIX.2
+(For strict compliance with POSIX.2, changing @code{MAKEOVERRIDES} does
+not affect @code{MAKEFLAGS} if the special target @samp{.POSIX} appears
+in the makefile.  You probably do not care about this.)
+
+@vindex MFLAGS
+A similar variable @code{MFLAGS} exists also, for historical
+compatibility.  It has the same value as @code{MAKEFLAGS} except that it
+does not contain the command line variable definitions, and it always
+begins with a hyphen unless it is empty (@code{MAKEFLAGS} begins with a
+hyphen only when it begins with an option that has no single-letter
+version, such as @samp{--warn-undefined-variables}).  @code{MFLAGS} was
+traditionally used explicitly in the recursive @code{make} command, like
+this:
+
+@example
+subsystem:
+        cd subdir && $(MAKE) $(MFLAGS)
+@end example
+
+@noindent
+but now @code{MAKEFLAGS} makes this usage redundant.  If you want your
+makefiles to be compatible with old @code{make} programs, use this
+technique; it will work fine with more modern @code{make} versions too.
+
+@cindex setting options from environment
+@cindex options, setting from environment
+@cindex setting options in makefiles
+@cindex options, setting in makefiles
+The @code{MAKEFLAGS} variable can also be useful if you want to have
+certain options, such as @samp{-k} (@pxref{Options Summary, ,Summary of
+Options}), set each time you run @code{make}.  You simply put a value for
+@code{MAKEFLAGS} in your environment.  You can also set @code{MAKEFLAGS} in
+a makefile, to specify additional flags that should also be in effect for
+that makefile.  (Note that you cannot use @code{MFLAGS} this way.  That
+variable is set only for compatibility; @code{make} does not interpret a
+value you set for it in any way.)
+
+When @code{make} interprets the value of @code{MAKEFLAGS} (either from the
+environment or from a makefile), it first prepends a hyphen if the value
+does not already begin with one.  Then it chops the value into words
+separated by blanks, and parses these words as if they were options given
+on the command line (except that @samp{-C}, @samp{-f}, @samp{-h},
+@samp{-o}, @samp{-W}, and their long-named versions are ignored; and there
+is no error for an invalid option).
+
+If you do put @code{MAKEFLAGS} in your environment, you should be sure not
+to include any options that will drastically affect the actions of
+@code{make} and undermine the purpose of makefiles and of @code{make}
+itself.  For instance, the @samp{-t}, @samp{-n}, and @samp{-q} options, if
+put in one of these variables, could have disastrous consequences and would
+certainly have at least surprising and probably annoying effects.@refill
+
+@node -w Option,  , Options/Recursion, Recursion
+@subsection The @samp{--print-directory} Option
+@cindex directories, printing them
+@cindex printing directories
+@cindex recursion, and printing directories
+
+If you use several levels of recursive @code{make} invocations, the
+@samp{-w} or @w{@samp{--print-directory}} option can make the output a
+lot easier to understand by showing each directory as @code{make}
+starts processing it and as @code{make} finishes processing it.  For
+example, if @samp{make -w} is run in the directory @file{/u/gnu/make},
+@code{make} will print a line of the form:@refill
+
+@example
+make: Entering directory `/u/gnu/make'.
+@end example
+
+@noindent
+before doing anything else, and a line of the form:
+
+@example
+make: Leaving directory `/u/gnu/make'.
+@end example
+
+@noindent
+when processing is completed.
+
+@cindex @code{-C}, and @code{-w}
+@cindex @code{--directory}, and @code{--print-directory}
+@cindex recursion, and @code{-w}
+@cindex @code{-w}, and @code{-C}
+@cindex @code{-w}, and recursion
+@cindex @code{--print-directory}, and @code{--directory}
+@cindex @code{--print-directory}, and recursion
+@cindex @code{--no-print-directory}
+@cindex @code{--print-directory}, disabling
+@cindex @code{-w}, disabling
+Normally, you do not need to specify this option because @samp{make}
+does it for you: @samp{-w} is turned on automatically when you use the
+@samp{-C} option, and in sub-@code{make}s.  @code{make} will not
+automatically turn on @samp{-w} if you also use @samp{-s}, which says to
+be silent, or if you use @samp{--no-print-directory} to explicitly
+disable it.
+
+@node Sequences, Empty Commands, Recursion, Commands
+@section Defining Canned Command Sequences
+@cindex sequences of commands
+@cindex commands, sequences of
+
+When the same sequence of commands is useful in making various targets, you
+can define it as a canned sequence with the @code{define} directive, and
+refer to the canned sequence from the rules for those targets.  The canned
+sequence is actually a variable, so the name must not conflict with other
+variable names.
+
+Here is an example of defining a canned sequence of commands:
+
+@example
+define run-yacc
+yacc $(firstword $^)
+mv y.tab.c $@@
+endef
+@end example
+@cindex @code{yacc}
+
+@noindent
+Here @code{run-yacc} is the name of the variable being defined;
+@code{endef} marks the end of the definition; the lines in between are the
+commands.  The @code{define} directive does not expand variable references
+and function calls in the canned sequence; the @samp{$} characters,
+parentheses, variable names, and so on, all become part of the value of the
+variable you are defining.
+@xref{Defining, ,Defining Variables Verbatim},
+for a complete explanation of @code{define}.
+
+The first command in this example runs Yacc on the first prerequisite of
+whichever rule uses the canned sequence.  The output file from Yacc is
+always named @file{y.tab.c}.  The second command moves the output to the
+rule's target file name.
+
+To use the canned sequence, substitute the variable into the commands of a
+rule.  You can substitute it like any other variable
+(@pxref{Reference, ,Basics of Variable References}).
+Because variables defined by @code{define} are recursively expanded
+variables, all the variable references you wrote inside the @code{define}
+are expanded now.  For example:
+
+@example
+foo.c : foo.y
+        $(run-yacc)
+@end example
+
+@noindent
+@samp{foo.y} will be substituted for the variable @samp{$^} when it occurs in
+@code{run-yacc}'s value, and @samp{foo.c} for @samp{$@@}.@refill
+
+This is a realistic example, but this particular one is not needed in
+practice because @code{make} has an implicit rule to figure out these
+commands based on the file names involved
+(@pxref{Implicit Rules, ,Using Implicit Rules}).
+
+@cindex @@, and @code{define}
+@cindex -, and @code{define}
+@cindex +, and @code{define}
+In command execution, each line of a canned sequence is treated just as
+if the line appeared on its own in the rule, preceded by a tab.  In
+particular, @code{make} invokes a separate subshell for each line.  You
+can use the special prefix characters that affect command lines
+(@samp{@@}, @samp{-}, and @samp{+}) on each line of a canned sequence.
+@xref{Commands, ,Writing the Commands in Rules}.
+For example, using this canned sequence:
+
+@example
+define frobnicate
+@@echo "frobnicating target $@@"
+frob-step-1 $< -o $@@-step-1
+frob-step-2 $@@-step-1 -o $@@
+endef
+@end example
+
+@noindent
+@code{make} will not echo the first line, the @code{echo} command.
+But it @emph{will} echo the following two command lines.
+
+On the other hand, prefix characters on the command line that refers to
+a canned sequence apply to every line in the sequence.  So the rule:
+
+@example
+frob.out: frob.in
+        @@$(frobnicate)
+@end example
+
+@noindent
+does not echo @emph{any} commands.
+(@xref{Echoing, ,Command Echoing}, for a full explanation of @samp{@@}.)
+
+@node Empty Commands,  , Sequences, Commands
+@section Using Empty Commands
+@cindex empty commands
+@cindex commands, empty
+
+It is sometimes useful to define commands which do nothing.  This is done
+simply by giving a command that consists of nothing but whitespace.  For
+example:
+
+@example
+target: ;
+@end example
+
+@noindent
+defines an empty command string for @file{target}.  You could also use a
+line beginning with a tab character to define an empty command string,
+but this would be confusing because such a line looks empty.
+
+@findex .DEFAULT@r{, and empty commands}
+You may be wondering why you would want to define a command string that
+does nothing.  The only reason this is useful is to prevent a target
+from getting implicit commands (from implicit rules or the
+@code{.DEFAULT} special target; @pxref{Implicit Rules} and
+@pxref{Last Resort, ,Defining Last-Resort Default Rules}).@refill
+
+@c !!! another reason is for canonical stamp files:
+@ignore
+foo: stamp-foo ;
+stamp-foo: foo.in
+        create foo frm foo.in
+        touch $@
+@end ignore
+
+You may be inclined to define empty command strings for targets that are
+not actual files, but only exist so that their prerequisites can be
+remade.  However, this is not the best way to do that, because the
+prerequisites may not be remade properly if the target file actually does exist.
+@xref{Phony Targets, ,Phony Targets}, for a better way to do this.
+
+@node Using Variables, Conditionals, Commands, Top
+@chapter How to Use Variables
+@cindex variable
+@cindex value
+@cindex recursive variable expansion
+@cindex simple variable expansion
+
+A @dfn{variable} is a name defined in a makefile to represent a string
+of text, called the variable's @dfn{value}.  These values are
+substituted by explicit request into targets, prerequisites, commands,
+and other parts of the makefile.  (In some other versions of @code{make},
+variables are called @dfn{macros}.)
+@cindex macro
+
+Variables and functions in all parts of a makefile are expanded when
+read, except for the shell commands in rules, the right-hand sides of
+variable definitions using @samp{=}, and the bodies of variable
+definitions using the @code{define} directive.@refill
+
+Variables can represent lists of file names, options to pass to compilers,
+programs to run, directories to look in for source files, directories to
+write output in, or anything else you can imagine.
+
+A variable name may be any sequence of characters not containing @samp{:},
+@samp{#}, @samp{=}, or leading or trailing whitespace.  However,
+variable names containing characters other than letters, numbers, and
+underscores should be avoided, as they may be given special meanings in the
+future, and with some shells they cannot be passed through the environment to a
+sub-@code{make}
+(@pxref{Variables/Recursion, ,Communicating Variables to a Sub-@code{make}}).
+
+Variable names are case-sensitive.  The names @samp{foo}, @samp{FOO},
+and @samp{Foo} all refer to different variables.
+
+It is traditional to use upper case letters in variable names, but we
+recommend using lower case letters for variable names that serve internal
+purposes in the makefile, and reserving upper case for parameters that
+control implicit rules or for parameters that the user should override with
+command options (@pxref{Overriding, ,Overriding Variables}).
+
+A few variables have names that are a single punctuation character or
+just a few characters.  These are the @dfn{automatic variables}, and
+they have particular specialized uses.  @xref{Automatic, ,Automatic Variables}.
+
+@menu
+* Reference::                   How to use the value of a variable.
+* Flavors::                     Variables come in two flavors.
+* Advanced::                    Advanced features for referencing a variable.
+* Values::                      All the ways variables get their values.
+* Setting::                     How to set a variable in the makefile.
+* Appending::                   How to append more text to the old value
+                                  of a variable.
+* Override Directive::          How to set a variable in the makefile even if
+                                  the user has set it with a command argument.
+* Defining::                    An alternate way to set a variable
+                                  to a verbatim string.
+* Environment::                 Variable values can come from the environment.
+* Target-specific::             Variable values can be defined on a per-target
+                                  basis.
+* Pattern-specific::            Target-specific variable values can be applied
+                                  to a group of targets that match a pattern.
+@end menu
+
+@node Reference, Flavors, Using Variables, Using Variables
+@section Basics of Variable References
+@cindex variables, how to reference
+@cindex reference to variables
+@cindex @code{$}, in variable reference
+@cindex dollar sign (@code{$}), in variable reference
+
+To substitute a variable's value, write a dollar sign followed by the name
+of the variable in parentheses or braces: either @samp{$(foo)} or
+@samp{$@{foo@}} is a valid reference to the variable @code{foo}.  This
+special significance of @samp{$} is why you must write @samp{$$} to have
+the effect of a single dollar sign in a file name or command.
+
+Variable references can be used in any context: targets, prerequisites,
+commands, most directives, and new variable values.  Here is an
+example of a common case, where a variable holds the names of all the
+object files in a program:
+
+@example
+@group
+objects = program.o foo.o utils.o
+program : $(objects)
+        cc -o program $(objects)
+
+$(objects) : defs.h
+@end group
+@end example
+
+Variable references work by strict textual substitution.  Thus, the rule
+
+@example
+@group
+foo = c
+prog.o : prog.$(foo)
+        $(foo)$(foo) -$(foo) prog.$(foo)
+@end group
+@end example
+
+@noindent
+could be used to compile a C program @file{prog.c}.  Since spaces before
+the variable value are ignored in variable assignments, the value of
+@code{foo} is precisely @samp{c}.  (Don't actually write your makefiles
+this way!)
+
+A dollar sign followed by a character other than a dollar sign,
+open-parenthesis or open-brace treats that single character as the
+variable name.  Thus, you could reference the variable @code{x} with
+@samp{$x}.  However, this practice is strongly discouraged, except in
+the case of the automatic variables (@pxref{Automatic, ,Automatic Variables}).
+
+@node Flavors, Advanced, Reference, Using Variables
+@section The Two Flavors of Variables
+@cindex flavors of variables
+@cindex recursive variable expansion
+@cindex variables, flavors
+@cindex recursively expanded variables
+@cindex variables, recursively expanded
+
+There are two ways that a variable in GNU @code{make} can have a value;
+we call them the two @dfn{flavors} of variables.  The two flavors are
+distinguished in how they are defined and in what they do when expanded.
+
+@cindex =
+The first flavor of variable is a @dfn{recursively expanded} variable.
+Variables of this sort are defined by lines using @samp{=}
+(@pxref{Setting, ,Setting Variables}) or by the @code{define} directive
+(@pxref{Defining, ,Defining Variables Verbatim}).  The value you specify
+is installed verbatim; if it contains references to other variables,
+these references are expanded whenever this variable is substituted (in
+the course of expanding some other string).  When this happens, it is
+called @dfn{recursive expansion}.@refill
+
+For example,
+
+@example
+foo = $(bar)
+bar = $(ugh)
+ugh = Huh?
+
+all:;echo $(foo)
+@end example
+
+@noindent
+will echo @samp{Huh?}: @samp{$(foo)} expands to @samp{$(bar)} which
+expands to @samp{$(ugh)} which finally expands to @samp{Huh?}.@refill
+
+This flavor of variable is the only sort supported by other versions of
+@code{make}.  It has its advantages and its disadvantages.  An advantage
+(most would say) is that:
+
+@example
+CFLAGS = $(include_dirs) -O
+include_dirs = -Ifoo -Ibar
+@end example
+
+@noindent
+will do what was intended: when @samp{CFLAGS} is expanded in a command,
+it will expand to @samp{-Ifoo -Ibar -O}.  A major disadvantage is that you
+cannot append something on the end of a variable, as in
+
+@example
+CFLAGS = $(CFLAGS) -O
+@end example
+
+@noindent
+because it will cause an infinite loop in the variable expansion.
+(Actually @code{make} detects the infinite loop and reports an error.)
+@cindex loops in variable expansion
+@cindex variables, loops in expansion
+
+Another disadvantage is that any functions
+(@pxref{Functions, ,Functions for Transforming Text})
+referenced in the definition will be executed every time the variable is
+expanded.  This makes @code{make} run slower; worse, it causes the
+@code{wildcard} and @code{shell} functions to give unpredictable results
+because you cannot easily control when they are called, or even how many
+times.
+
+To avoid all the problems and inconveniences of recursively expanded
+variables, there is another flavor: simply expanded variables.
+
+@cindex simply expanded variables
+@cindex variables, simply expanded
+@cindex :=
+@dfn{Simply expanded variables} are defined by lines using @samp{:=}
+(@pxref{Setting, ,Setting Variables}).
+The value of a simply expanded variable is scanned
+once and for all, expanding any references to other variables and
+functions, when the variable is defined.  The actual value of the simply
+expanded variable is the result of expanding the text that you write.
+It does not contain any references to other variables; it contains their
+values @emph{as of the time this variable was defined}.  Therefore,
+
+@example
+x := foo
+y := $(x) bar
+x := later
+@end example
+
+@noindent
+is equivalent to
+
+@example
+y := foo bar
+x := later
+@end example
+
+When a simply expanded variable is referenced, its value is substituted
+verbatim.
+
+Here is a somewhat more complicated example, illustrating the use of
+@samp{:=} in conjunction with the @code{shell} function.
+(@xref{Shell Function, , The @code{shell} Function}.)  This example
+also shows use of the variable @code{MAKELEVEL}, which is changed
+when it is passed down from level to level.
+(@xref{Variables/Recursion, , Communicating Variables to a
+Sub-@code{make}}, for information about @code{MAKELEVEL}.)
+
+@vindex MAKELEVEL
+@vindex MAKE
+@example
+@group
+ifeq (0,$@{MAKELEVEL@})
+cur-dir   := $(shell pwd)
+whoami    := $(shell whoami)
+host-type := $(shell arch)
+MAKE := $@{MAKE@} host-type=$@{host-type@} whoami=$@{whoami@}
+endif
+@end group
+@end example
+
+@noindent
+An advantage of this use of @samp{:=} is that a typical
+`descend into a directory' command then looks like this:
+
+@example
+@group
+$@{subdirs@}:
+      $@{MAKE@} cur-dir=$@{cur-dir@}/$@@ -C $@@ all
+@end group
+@end example
+
+Simply expanded variables generally make complicated makefile programming
+more predictable because they work like variables in most programming
+languages.  They allow you to redefine a variable using its own value (or
+its value processed in some way by one of the expansion functions) and to
+use the expansion functions much more efficiently
+(@pxref{Functions, ,Functions for Transforming Text}).
+
+@cindex spaces, in variable values
+@cindex whitespace, in variable values
+@cindex variables, spaces in values
+You can also use them to introduce controlled leading whitespace into
+variable values.  Leading whitespace characters are discarded from your
+input before substitution of variable references and function calls;
+this means you can include leading spaces in a variable value by
+protecting them with variable references, like this:
+
+@example
+nullstring :=
+space := $(nullstring) # end of the line
+@end example
+
+@noindent
+Here the value of the variable @code{space} is precisely one space.  The
+comment @w{@samp{# end of the line}} is included here just for clarity.
+Since trailing space characters are @emph{not} stripped from variable
+values, just a space at the end of the line would have the same effect
+(but be rather hard to read).  If you put whitespace at the end of a
+variable value, it is a good idea to put a comment like that at the end
+of the line to make your intent clear.  Conversely, if you do @emph{not}
+want any whitespace characters at the end of your variable value, you
+must remember not to put a random comment on the end of the line after
+some whitespace, such as this:
+
+@example
+dir := /foo/bar    # directory to put the frobs in
+@end example
+
+@noindent
+Here the value of the variable @code{dir} is @w{@samp{/foo/bar    }}
+(with four trailing spaces), which was probably not the intention.
+(Imagine something like @w{@samp{$(dir)/file}} with this definition!)
+
+@cindex conditional variable assignment
+@cindex variables, conditional assignment
+@cindex ?=
+There is another assignment operator for variables, @samp{?=}.  This
+is called a conditional variable assignment operator, because it only
+has an effect if the variable is not yet defined.  This statement:
+
+@example
+FOO ?= bar
+@end example
+
+@noindent
+is exactly equivalent to this
+(@pxref{Origin Function, ,The @code{origin} Function}):
+
+@example
+ifeq ($(origin FOO), undefined)
+  FOO = bar
+endif
+@end example
+
+Note that a variable set to an empty value is still defined, so
+@samp{?=} will not set that variable.
+
+@node Advanced, Values, Flavors, Using Variables
+@section Advanced Features for Reference to Variables
+@cindex reference to variables
+
+This section describes some advanced features you can use to reference
+variables in more flexible ways.
+
+@menu
+* Substitution Refs::           Referencing a variable with
+                                  substitutions on the value.
+* Computed Names::              Computing the name of the variable to refer to.
+@end menu
+
+@node Substitution Refs, Computed Names, Advanced, Advanced
+@subsection Substitution References
+@cindex modified variable reference
+@cindex substitution variable reference
+@cindex variables, modified reference
+@cindex variables, substitution reference
+
+@cindex variables, substituting suffix in
+@cindex suffix, substituting in variables
+A @dfn{substitution reference} substitutes the value of a variable with
+alterations that you specify.  It has the form
+@samp{$(@var{var}:@var{a}=@var{b})} (or
+@samp{$@{@var{var}:@var{a}=@var{b}@}}) and its meaning is to take the value
+of the variable @var{var}, replace every @var{a} at the end of a word with
+@var{b} in that value, and substitute the resulting string.
+
+When we say ``at the end of a word'', we mean that @var{a} must appear
+either followed by whitespace or at the end of the value in order to be
+replaced; other occurrences of @var{a} in the value are unaltered.  For
+example:@refill
+
+@example
+foo := a.o b.o c.o
+bar := $(foo:.o=.c)
+@end example
+
+@noindent
+sets @samp{bar} to @samp{a.c b.c c.c}.  @xref{Setting, ,Setting Variables}.
+
+A substitution reference is actually an abbreviation for use of the
+@code{patsubst} expansion function (@pxref{Text Functions, ,Functions for String Substitution and Analysis}).  We provide
+substitution references as well as @code{patsubst} for compatibility with
+other implementations of @code{make}.
+
+@findex patsubst
+Another type of substitution reference lets you use the full power of
+the @code{patsubst} function.  It has the same form
+@samp{$(@var{var}:@var{a}=@var{b})} described above, except that now
+@var{a} must contain a single @samp{%} character.  This case is
+equivalent to @samp{$(patsubst @var{a},@var{b},$(@var{var}))}.
+@xref{Text Functions, ,Functions for String Substitution and Analysis},
+for a description of the @code{patsubst} function.@refill
+
+@example
+@group
+@exdent For example:
+
+foo := a.o b.o c.o
+bar := $(foo:%.o=%.c)
+@end group
+@end example
+
+@noindent
+sets @samp{bar} to @samp{a.c b.c c.c}.
+
+@node Computed Names,  , Substitution Refs, Advanced
+@subsection Computed Variable Names
+@cindex nested variable reference
+@cindex computed variable name
+@cindex variables, computed names
+@cindex variables, nested references
+@cindex variables, @samp{$} in name
+@cindex @code{$}, in variable name
+@cindex dollar sign (@code{$}), in variable name
+
+Computed variable names are a complicated concept needed only for
+sophisticated makefile programming.  For most purposes you need not
+consider them, except to know that making a variable with a dollar sign
+in its name might have strange results.  However, if you are the type
+that wants to understand everything, or you are actually interested in
+what they do, read on.
+
+Variables may be referenced inside the name of a variable.  This is
+called a @dfn{computed variable name} or a @dfn{nested variable
+reference}.  For example,
+
+@example
+x = y
+y = z
+a := $($(x))
+@end example
+
+@noindent
+defines @code{a} as @samp{z}: the @samp{$(x)} inside @samp{$($(x))} expands
+to @samp{y}, so @samp{$($(x))} expands to @samp{$(y)} which in turn expands
+to @samp{z}.  Here the name of the variable to reference is not stated
+explicitly; it is computed by expansion of @samp{$(x)}.  The reference
+@samp{$(x)} here is nested within the outer variable reference.
+
+The previous example shows two levels of nesting, but any number of levels
+is possible.  For example, here are three levels:
+
+@example
+x = y
+y = z
+z = u
+a := $($($(x)))
+@end example
+
+@noindent
+Here the innermost @samp{$(x)} expands to @samp{y}, so @samp{$($(x))}
+expands to @samp{$(y)} which in turn expands to @samp{z}; now we have
+@samp{$(z)}, which becomes @samp{u}.
+
+References to recursively-expanded variables within a variable name are
+reexpanded in the usual fashion.  For example:
+
+@example
+x = $(y)
+y = z
+z = Hello
+a := $($(x))
+@end example
+
+@noindent
+defines @code{a} as @samp{Hello}: @samp{$($(x))} becomes @samp{$($(y))}
+which becomes @samp{$(z)} which becomes @samp{Hello}.
+
+Nested variable references can also contain modified references and
+function invocations (@pxref{Functions, ,Functions for Transforming Text}),
+just like any other reference.
+For example, using the @code{subst} function
+(@pxref{Text Functions, ,Functions for String Substitution and Analysis}):
+
+@example
+@group
+x = variable1
+variable2 := Hello
+y = $(subst 1,2,$(x))
+z = y
+a := $($($(z)))
+@end group
+@end example
+
+@noindent
+eventually defines @code{a} as @samp{Hello}.  It is doubtful that anyone
+would ever want to write a nested reference as convoluted as this one, but
+it works: @samp{$($($(z)))} expands to @samp{$($(y))} which becomes
+@samp{$($(subst 1,2,$(x)))}.  This gets the value @samp{variable1} from
+@code{x} and changes it by substitution to @samp{variable2}, so that the
+entire string becomes @samp{$(variable2)}, a simple variable reference
+whose value is @samp{Hello}.@refill
+
+A computed variable name need not consist entirely of a single variable
+reference.  It can contain several variable references, as well as some
+invariant text.  For example,
+
+@example
+@group
+a_dirs := dira dirb
+1_dirs := dir1 dir2
+@end group
+
+@group
+a_files := filea fileb
+1_files := file1 file2
+@end group
+
+@group
+ifeq "$(use_a)" "yes"
+a1 := a
+else
+a1 := 1
+endif
+@end group
+
+@group
+ifeq "$(use_dirs)" "yes"
+df := dirs
+else
+df := files
+endif
+
+dirs := $($(a1)_$(df))
+@end group
+@end example
+
+@noindent
+will give @code{dirs} the same value as @code{a_dirs}, @code{1_dirs},
+@code{a_files} or @code{1_files} depending on the settings of @code{use_a}
+and @code{use_dirs}.@refill
+
+Computed variable names can also be used in substitution references:
+
+@example
+@group
+a_objects := a.o b.o c.o
+1_objects := 1.o 2.o 3.o
+
+sources := $($(a1)_objects:.o=.c)
+@end group
+@end example
+
+@noindent
+defines @code{sources} as either @samp{a.c b.c c.c} or @samp{1.c 2.c 3.c},
+depending on the value of @code{a1}.
+
+The only restriction on this sort of use of nested variable references
+is that they cannot specify part of the name of a function to be called.
+This is because the test for a recognized function name is done before
+the expansion of nested references.  For example,
+
+@example
+@group
+ifdef do_sort
+func := sort
+else
+func := strip
+endif
+@end group
+
+@group
+bar := a d b g q c
+@end group
+
+@group
+foo := $($(func) $(bar))
+@end group
+@end example
+
+@noindent
+attempts to give @samp{foo} the value of the variable @samp{sort a d b g
+q c} or @samp{strip a d b g q c}, rather than giving @samp{a d b g q c}
+as the argument to either the @code{sort} or the @code{strip} function.
+This restriction could be removed in the future if that change is shown
+to be a good idea.
+
+You can also use computed variable names in the left-hand side of a
+variable assignment, or in a @code{define} directive, as in:
+
+@example
+dir = foo
+$(dir)_sources := $(wildcard $(dir)/*.c)
+define $(dir)_print
+lpr $($(dir)_sources)
+endef
+@end example
+
+@noindent
+This example defines the variables @samp{dir}, @samp{foo_sources}, and
+@samp{foo_print}.
+
+Note that @dfn{nested variable references} are quite different from
+@dfn{recursively expanded variables}
+(@pxref{Flavors, ,The Two Flavors of Variables}), though both are
+used together in complex ways when doing makefile programming.@refill
+
+@node Values, Setting, Advanced, Using Variables
+@section How Variables Get Their Values
+@cindex variables, how they get their values
+@cindex value, how a variable gets it
+
+Variables can get values in several different ways:
+
+@itemize @bullet
+@item
+You can specify an overriding value when you run @code{make}.
+@xref{Overriding, ,Overriding Variables}.
+
+@item
+You can specify a value in the makefile, either
+with an assignment (@pxref{Setting, ,Setting Variables}) or with a
+verbatim definition (@pxref{Defining, ,Defining Variables Verbatim}).@refill
+
+@item
+Variables in the environment become @code{make} variables.
+@xref{Environment, ,Variables from the Environment}.
+
+@item
+Several @dfn{automatic} variables are given new values for each rule.
+Each of these has a single conventional use.
+@xref{Automatic, ,Automatic Variables}.
+
+@item
+Several variables have constant initial values.
+@xref{Implicit Variables, ,Variables Used by Implicit Rules}.
+@end itemize
+
+@node Setting, Appending, Values, Using Variables
+@section Setting Variables
+@cindex setting variables
+@cindex variables, setting
+@cindex =
+@cindex :=
+@cindex ?=
+
+To set a variable from the makefile, write a line starting with the
+variable name followed by @samp{=} or @samp{:=}.  Whatever follows the
+@samp{=} or @samp{:=} on the line becomes the value.  For example,
+
+@example
+objects = main.o foo.o bar.o utils.o
+@end example
+
+@noindent
+defines a variable named @code{objects}.  Whitespace around the variable
+name and immediately after the @samp{=} is ignored.
+
+Variables defined with @samp{=} are @dfn{recursively expanded} variables.
+Variables defined with @samp{:=} are @dfn{simply expanded} variables; these
+definitions can contain variable references which will be expanded before
+the definition is made.  @xref{Flavors, ,The Two Flavors of Variables}.
+
+The variable name may contain function and variable references, which
+are expanded when the line is read to find the actual variable name to use.
+
+There is no limit on the length of the value of a variable except the
+amount of swapping space on the computer.  When a variable definition is
+long, it is a good idea to break it into several lines by inserting
+backslash-newline at convenient places in the definition.  This will not
+affect the functioning of @code{make}, but it will make the makefile easier
+to read.
+
+Most variable names are considered to have the empty string as a value if
+you have never set them.  Several variables have built-in initial values
+that are not empty, but you can set them in the usual ways
+(@pxref{Implicit Variables, ,Variables Used by Implicit Rules}).
+Several special variables are set
+automatically to a new value for each rule; these are called the
+@dfn{automatic} variables (@pxref{Automatic, ,Automatic Variables}).
+
+If you'd like a variable to be set to a value only if it's not already
+set, then you can use the shorthand operator @samp{?=} instead of
+@samp{=}.  These two settings of the variable @samp{FOO} are identical
+(@pxref{Origin Function, ,The @code{origin} Function}):
+
+@example
+FOO ?= bar
+@end example
+
+@noindent
+and
+
+@example
+ifeq ($(origin FOO), undefined)
+FOO = bar
+endif
+@end example
+
+@node Appending, Override Directive, Setting, Using Variables
+@section Appending More Text to Variables
+@cindex +=
+@cindex appending to variables
+@cindex variables, appending to
+
+Often it is useful to add more text to the value of a variable already defined.
+You do this with a line containing @samp{+=}, like this:
+
+@example
+objects += another.o
+@end example
+
+@noindent
+This takes the value of the variable @code{objects}, and adds the text
+@samp{another.o} to it (preceded by a single space).  Thus:
+
+@example
+objects = main.o foo.o bar.o utils.o
+objects += another.o
+@end example
+
+@noindent
+sets @code{objects} to @samp{main.o foo.o bar.o utils.o another.o}.
+
+Using @samp{+=} is similar to:
+
+@example
+objects = main.o foo.o bar.o utils.o
+objects := $(objects) another.o
+@end example
+
+@noindent
+but differs in ways that become important when you use more complex values.
+
+When the variable in question has not been defined before, @samp{+=}
+acts just like normal @samp{=}: it defines a recursively-expanded
+variable.  However, when there @emph{is} a previous definition, exactly
+what @samp{+=} does depends on what flavor of variable you defined
+originally.  @xref{Flavors, ,The Two Flavors of Variables}, for an
+explanation of the two flavors of variables.
+
+When you add to a variable's value with @samp{+=}, @code{make} acts
+essentially as if you had included the extra text in the initial
+definition of the variable.  If you defined it first with @samp{:=},
+making it a simply-expanded variable, @samp{+=} adds to that
+simply-expanded definition, and expands the new text before appending it
+to the old value just as @samp{:=} does
+(@pxref{Setting, ,Setting Variables}, for a full explanation of @samp{:=}).
+In fact,
+
+@example
+variable := value
+variable += more
+@end example
+
+@noindent
+is exactly equivalent to:
+
+@noindent
+@example
+variable := value
+variable := $(variable) more
+@end example
+
+On the other hand, when you use @samp{+=} with a variable that you defined
+first to be recursively-expanded using plain @samp{=}, @code{make} does
+something a bit different.  Recall that when you define a
+recursively-expanded variable, @code{make} does not expand the value you set
+for variable and function references immediately.  Instead it stores the text
+verbatim, and saves these variable and function references to be expanded
+later, when you refer to the new variable (@pxref{Flavors, ,The Two Flavors
+of Variables}).  When you use @samp{+=} on a recursively-expanded variable,
+it is this unexpanded text to which @code{make} appends the new text you
+specify.
+
+@example
+@group
+variable = value
+variable += more
+@end group
+@end example
+
+@noindent
+is roughly equivalent to:
+
+@example
+@group
+temp = value
+variable = $(temp) more
+@end group
+@end example
+
+@noindent
+except that of course it never defines a variable called @code{temp}.
+The importance of this comes when the variable's old value contains
+variable references.  Take this common example:
+
+@example
+CFLAGS = $(includes) -O
+@dots{}
+CFLAGS += -pg # enable profiling
+@end example
+
+@noindent
+The first line defines the @code{CFLAGS} variable with a reference to another
+variable, @code{includes}.  (@code{CFLAGS} is used by the rules for C
+compilation; @pxref{Catalogue of Rules, ,Catalogue of Implicit Rules}.)
+Using @samp{=} for the definition makes @code{CFLAGS} a recursively-expanded
+variable, meaning @w{@samp{$(includes) -O}} is @emph{not} expanded when
+@code{make} processes the definition of @code{CFLAGS}.  Thus, @code{includes}
+need not be defined yet for its value to take effect.  It only has to be
+defined before any reference to @code{CFLAGS}.  If we tried to append to the
+value of @code{CFLAGS} without using @samp{+=}, we might do it like this:
+
+@example
+CFLAGS := $(CFLAGS) -pg # enable profiling
+@end example
+
+@noindent
+This is pretty close, but not quite what we want.  Using @samp{:=}
+redefines @code{CFLAGS} as a simply-expanded variable; this means
+@code{make} expands the text @w{@samp{$(CFLAGS) -pg}} before setting the
+variable.  If @code{includes} is not yet defined, we get @w{@samp{ -O
+-pg}}, and a later definition of @code{includes} will have no effect.
+Conversely, by using @samp{+=} we set @code{CFLAGS} to the
+@emph{unexpanded} value @w{@samp{$(includes) -O -pg}}.  Thus we preserve
+the reference to @code{includes}, so if that variable gets defined at
+any later point, a reference like @samp{$(CFLAGS)} still uses its
+value.
+
+@node Override Directive, Defining, Appending, Using Variables
+@section The @code{override} Directive
+@findex override
+@cindex overriding with @code{override}
+@cindex variables, overriding
+
+If a variable has been set with a command argument
+(@pxref{Overriding, ,Overriding Variables}),
+then ordinary assignments in the makefile are ignored.  If you want to set
+the variable in the makefile even though it was set with a command
+argument, you can use an @code{override} directive, which is a line that
+looks like this:@refill
+
+@example
+override @var{variable} = @var{value}
+@end example
+
+@noindent
+or
+
+@example
+override @var{variable} := @var{value}
+@end example
+
+To append more text to a variable defined on the command line, use:
+
+@example
+override @var{variable} += @var{more text}
+@end example
+
+@noindent
+@xref{Appending, ,Appending More Text to Variables}.
+
+The @code{override} directive was not invented for escalation in the war
+between makefiles and command arguments.  It was invented so you can alter
+and add to values that the user specifies with command arguments.
+
+For example, suppose you always want the @samp{-g} switch when you run the
+C compiler, but you would like to allow the user to specify the other
+switches with a command argument just as usual.  You could use this
+@code{override} directive:
+
+@example
+override CFLAGS += -g
+@end example
+
+You can also use @code{override} directives with @code{define} directives.
+This is done as you might expect:
+
+@example
+override define foo
+bar
+endef
+@end example
+
+@noindent
+@iftex
+See the next section for information about @code{define}.
+@end iftex
+@ifinfo
+@xref{Defining, ,Defining Variables Verbatim}.
+@end ifinfo
+
+@node Defining, Environment, Override Directive, Using Variables
+@section Defining Variables Verbatim
+@findex define
+@findex endef
+@cindex verbatim variable definition
+@cindex defining variables verbatim
+@cindex variables, defining verbatim
+
+Another way to set the value of a variable is to use the @code{define}
+directive.  This directive has an unusual syntax which allows newline
+characters to be included in the value, which is convenient for defining
+both canned sequences of commands
+(@pxref{Sequences, ,Defining Canned Command Sequences}), and also
+sections of makefile syntax to use with @code{eval} (@pxref{Eval Function}).
+
+The @code{define} directive is followed on the same line by the name of the
+variable and nothing more.  The value to give the variable appears on the
+following lines.  The end of the value is marked by a line containing just
+the word @code{endef}.  Aside from this difference in syntax, @code{define}
+works just like @samp{=}: it creates a recursively-expanded variable
+(@pxref{Flavors, ,The Two Flavors of Variables}).
+The variable name may contain function and variable references, which
+are expanded when the directive is read to find the actual variable name
+to use.
+
+You may nest @code{define} directives: @code{make} will keep track of
+nested directives and report an error if they are not all properly
+closed with @code{endef}.  Note that lines beginning with tab
+characters are considered part of a command script, so any
+@code{define} or @code{endef} strings appearing on such a line will
+not be considered @code{make} operators.
+
+@example
+define two-lines
+echo foo
+echo $(bar)
+endef
+@end example
+
+The value in an ordinary assignment cannot contain a newline; but the
+newlines that separate the lines of the value in a @code{define} become
+part of the variable's value (except for the final newline which precedes
+the @code{endef} and is not considered part of the value).@refill
+
+@need 800
+When used in a command script, the previous example is functionally
+equivalent to this:
+
+@example
+two-lines = echo foo; echo $(bar)
+@end example
+
+@noindent
+since two commands separated by semicolon behave much like two separate
+shell commands.  However, note that using two separate lines means
+@code{make} will invoke the shell twice, running an independent subshell
+for each line.  @xref{Execution, ,Command Execution}.
+
+If you want variable definitions made with @code{define} to take
+precedence over command-line variable definitions, you can use the
+@code{override} directive together with @code{define}:
+
+@example
+override define two-lines
+foo
+$(bar)
+endef
+@end example
+
+@noindent
+@xref{Override Directive, ,The @code{override} Directive}.
+
+@node Environment, Target-specific, Defining, Using Variables
+@section Variables from the Environment
+
+@cindex variables, environment
+@cindex environment
+Variables in @code{make} can come from the environment in which
+@code{make} is run.  Every environment variable that @code{make} sees when
+it starts up is transformed into a @code{make} variable with the same name
+and value.  But an explicit assignment in the makefile, or with a command
+argument, overrides the environment.  (If the @samp{-e} flag is specified,
+then values from the environment override assignments in the makefile.
+@xref{Options Summary, ,Summary of Options}.
+But this is not recommended practice.)
+
+Thus, by setting the variable @code{CFLAGS} in your environment, you can
+cause all C compilations in most makefiles to use the compiler switches you
+prefer.  This is safe for variables with standard or conventional meanings
+because you know that no makefile will use them for other things.  (But
+this is not totally reliable; some makefiles set @code{CFLAGS} explicitly
+and therefore are not affected by the value in the environment.)
+
+When @code{make} is invoked recursively, variables defined in the
+outer invocation can be passed to inner invocations through the
+environment (@pxref{Recursion, ,Recursive Use of @code{make}}).  By
+default, only variables that came from the environment or the command
+line are passed to recursive invocations.  You can use the
+@code{export} directive to pass other variables.
+@xref{Variables/Recursion, , Communicating Variables to a
+Sub-@code{make}}, for full details.
+
+Other use of variables from the environment is not recommended.  It is not
+wise for makefiles to depend for their functioning on environment variables
+set up outside their control, since this would cause different users to get
+different results from the same makefile.  This is against the whole
+purpose of most makefiles.
+
+Such problems would be especially likely with the variable @code{SHELL},
+which is normally present in the environment to specify the user's choice
+of interactive shell.  It would be very undesirable for this choice to
+affect @code{make}.  So @code{make} ignores the environment value of
+@code{SHELL} (except on MS-DOS and MS-Windows, where @code{SHELL} is
+usually not set.  @xref{Execution, ,Special handling of SHELL on
+MS-DOS}.)@refill
+
+@node Target-specific, Pattern-specific, Environment, Using Variables
+@section Target-specific Variable Values
+@cindex target-specific variables
+@cindex variables, target-specific
+
+Variable values in @code{make} are usually global; that is, they are the
+same regardless of where they are evaluated (unless they're reset, of
+course).  One exception to that is automatic variables
+(@pxref{Automatic, ,Automatic Variables}).
+
+The other exception is @dfn{target-specific variable values}.  This
+feature allows you to define different values for the same variable,
+based on the target that @code{make} is currently building.  As with
+automatic variables, these values are only available within the context
+of a target's command script (and in other target-specific assignments).
+
+Set a target-specific variable value like this:
+
+@example
+@var{target} @dots{} : @var{variable-assignment}
+@end example
+
+@noindent
+or like this:
+
+@example
+@var{target} @dots{} : override @var{variable-assignment}
+@end example
+
+Multiple @var{target} values create a target-specific variable value for
+each member of the target list individually.
+
+The @var{variable-assignment} can be any valid form of assignment;
+recursive (@samp{=}), static (@samp{:=}), appending (@samp{+=}), or
+conditional (@samp{?=}).  All variables that appear within the
+@var{variable-assignment} are evaluated within the context of the
+target: thus, any previously-defined target-specific variable values
+will be in effect.  Note that this variable is actually distinct from
+any ``global'' value: the two variables do not have to have the same
+flavor (recursive vs. static).
+
+Target-specific variables have the same priority as any other makefile
+variable.  Variables provided on the command-line (and in the
+environment if the @samp{-e} option is in force) will take precedence.
+Specifying the @code{override} directive will allow the target-specific
+variable value to be preferred.
+
+There is one more special feature of target-specific variables: when you
+define a target-specific variable, that variable value is also in effect
+for all prerequisites of this target (unless those prerequisites override
+it with their own target-specific variable value).  So, for example, a
+statement like this:
+
+@example
+prog : CFLAGS = -g
+prog : prog.o foo.o bar.o
+@end example
+
+@noindent
+will set @code{CFLAGS} to @samp{-g} in the command script for
+@file{prog}, but it will also set @code{CFLAGS} to @samp{-g} in the
+command scripts that create @file{prog.o}, @file{foo.o}, and
+@file{bar.o}, and any command scripts which create their prerequisites.
+
+@node Pattern-specific,  , Target-specific, Using Variables
+@section Pattern-specific Variable Values
+@cindex pattern-specific variables
+@cindex variables, pattern-specific
+
+In addition to target-specific variable values (@pxref{Target-specific,
+,Target-specific Variable Values}), GNU @code{make} supports
+pattern-specific variable values.  In this form, a variable is defined
+for any target that matches the pattern specified.  Variables defined in
+this way are searched after any target-specific variables defined
+explicitly for that target, and before target-specific variables defined
+for the parent target.
+
+Set a pattern-specific variable value like this:
+
+@example
+@var{pattern} @dots{} : @var{variable-assignment}
+@end example
+
+@noindent
+or like this:
+
+@example
+@var{pattern} @dots{} : override @var{variable-assignment}
+@end example
+
+@noindent
+where @var{pattern} is a %-pattern.  As with target-specific variable
+values, multiple @var{pattern} values create a pattern-specific variable
+value for each pattern individually.  The @var{variable-assignment} can
+be any valid form of assignment.  Any command-line variable setting will
+take precedence, unless @code{override} is specified.
+
+For example:
+
+@example
+%.o : CFLAGS = -O
+@end example
+
+@noindent
+will assign @code{CFLAGS} the value of @samp{-O} for all targets
+matching the pattern @code{%.o}.
+
+@node Conditionals, Functions, Using Variables, Top
+@chapter Conditional Parts of Makefiles
+
+@cindex conditionals
+A @dfn{conditional} causes part of a makefile to be obeyed or ignored
+depending on the values of variables.  Conditionals can compare the
+value of one variable to another, or the value of a variable to
+a constant string.  Conditionals control what @code{make} actually
+``sees'' in the makefile, so they @emph{cannot} be used to control shell
+commands at the time of execution.@refill
+
+@menu
+* Conditional Example::         Example of a conditional
+* Conditional Syntax::          The syntax of conditionals.
+* Testing Flags::               Conditionals that test flags.
+@end menu
+
+@node Conditional Example, Conditional Syntax, Conditionals, Conditionals
+@section Example of a Conditional
+
+The following example of a conditional tells @code{make} to use one set
+of libraries if the @code{CC} variable is @samp{gcc}, and a different
+set of libraries otherwise.  It works by controlling which of two
+command lines will be used as the command for a rule.  The result is
+that @samp{CC=gcc} as an argument to @code{make} changes not only which
+compiler is used but also which libraries are linked.
+
+@example
+libs_for_gcc = -lgnu
+normal_libs =
+
+foo: $(objects)
+ifeq ($(CC),gcc)
+        $(CC) -o foo $(objects) $(libs_for_gcc)
+else
+        $(CC) -o foo $(objects) $(normal_libs)
+endif
+@end example
+
+This conditional uses three directives: one @code{ifeq}, one @code{else}
+and one @code{endif}.
+
+The @code{ifeq} directive begins the conditional, and specifies the
+condition.  It contains two arguments, separated by a comma and surrounded
+by parentheses.  Variable substitution is performed on both arguments and
+then they are compared.  The lines of the makefile following the
+@code{ifeq} are obeyed if the two arguments match; otherwise they are
+ignored.
+
+The @code{else} directive causes the following lines to be obeyed if the
+previous conditional failed.  In the example above, this means that the
+second alternative linking command is used whenever the first alternative
+is not used.  It is optional to have an @code{else} in a conditional.
+
+The @code{endif} directive ends the conditional.  Every conditional must
+end with an @code{endif}.  Unconditional makefile text follows.
+
+As this example illustrates, conditionals work at the textual level:
+the lines of the conditional are treated as part of the makefile, or
+ignored, according to the condition.  This is why the larger syntactic
+units of the makefile, such as rules, may cross the beginning or the
+end of the conditional.
+
+When the variable @code{CC} has the value @samp{gcc}, the above example has
+this effect:
+
+@example
+foo: $(objects)
+        $(CC) -o foo $(objects) $(libs_for_gcc)
+@end example
+
+@noindent
+When the variable @code{CC} has any other value, the effect is this:
+
+@example
+foo: $(objects)
+        $(CC) -o foo $(objects) $(normal_libs)
+@end example
+
+Equivalent results can be obtained in another way by conditionalizing a
+variable assignment and then using the variable unconditionally:
+
+@example
+libs_for_gcc = -lgnu
+normal_libs =
+
+ifeq ($(CC),gcc)
+  libs=$(libs_for_gcc)
+else
+  libs=$(normal_libs)
+endif
+
+foo: $(objects)
+        $(CC) -o foo $(objects) $(libs)
+@end example
+
+@node Conditional Syntax, Testing Flags, Conditional Example, Conditionals
+@section Syntax of Conditionals
+@findex ifdef
+@findex ifeq
+@findex ifndef
+@findex ifneq
+@findex else
+@findex endif
+
+The syntax of a simple conditional with no @code{else} is as follows:
+
+@example
+@var{conditional-directive}
+@var{text-if-true}
+endif
+@end example
+
+@noindent
+The @var{text-if-true} may be any lines of text, to be considered as part
+of the makefile if the condition is true.  If the condition is false, no
+text is used instead.
+
+The syntax of a complex conditional is as follows:
+
+@example
+@var{conditional-directive}
+@var{text-if-true}
+else
+@var{text-if-false}
+endif
+@end example
+
+@noindent
+If the condition is true, @var{text-if-true} is used; otherwise,
+@var{text-if-false} is used instead.  The @var{text-if-false} can be any
+number of lines of text.
+
+The syntax of the @var{conditional-directive} is the same whether the
+conditional is simple or complex.  There are four different directives that
+test different conditions.  Here is a table of them:
+
+@table @code
+@item ifeq (@var{arg1}, @var{arg2})
+@itemx ifeq '@var{arg1}' '@var{arg2}'
+@itemx ifeq "@var{arg1}" "@var{arg2}"
+@itemx ifeq "@var{arg1}" '@var{arg2}'
+@itemx ifeq '@var{arg1}' "@var{arg2}"
+Expand all variable references in @var{arg1} and @var{arg2} and
+compare them.  If they are identical, the @var{text-if-true} is
+effective; otherwise, the @var{text-if-false}, if any, is effective.
+
+Often you want to test if a variable has a non-empty value.  When the
+value results from complex expansions of variables and functions,
+expansions you would consider empty may actually contain whitespace
+characters and thus are not seen as empty.  However, you can use the
+@code{strip} function (@pxref{Text Functions}) to avoid interpreting
+whitespace as a non-empty value.  For example:
+
+@example
+@group
+ifeq ($(strip $(foo)),)
+@var{text-if-empty}
+endif
+@end group
+@end example
+
+@noindent
+will evaluate @var{text-if-empty} even if the expansion of
+@code{$(foo)} contains whitespace characters.
+
+@item ifneq (@var{arg1}, @var{arg2})
+@itemx ifneq '@var{arg1}' '@var{arg2}'
+@itemx ifneq "@var{arg1}" "@var{arg2}"
+@itemx ifneq "@var{arg1}" '@var{arg2}'
+@itemx ifneq '@var{arg1}' "@var{arg2}"
+Expand all variable references in @var{arg1} and @var{arg2} and
+compare them.  If they are different, the @var{text-if-true} is
+effective; otherwise, the @var{text-if-false}, if any, is effective.
+
+@item ifdef @var{variable-name}
+If the variable @var{variable-name} has a non-empty value, the
+@var{text-if-true} is effective; otherwise, the @var{text-if-false},
+if any, is effective.  Variables that have never been defined have an
+empty value.
+
+Note that @code{ifdef} only tests whether a variable has a value.  It
+does not expand the variable to see if that value is nonempty.
+Consequently, tests using @code{ifdef} return true for all definitions
+except those like @code{foo =}.  To test for an empty value, use
+@w{@code{ifeq ($(foo),)}}.  For example,
+
+@example
+bar =
+foo = $(bar)
+ifdef foo
+frobozz = yes
+else
+frobozz = no
+endif
+@end example
+
+@noindent
+sets @samp{frobozz} to @samp{yes}, while:
+
+@example
+foo =
+ifdef foo
+frobozz = yes
+else
+frobozz = no
+endif
+@end example
+
+@noindent
+sets @samp{frobozz} to @samp{no}.
+
+@item ifndef @var{variable-name}
+If the variable @var{variable-name} has an empty value, the
+@var{text-if-true} is effective; otherwise, the @var{text-if-false},
+if any, is effective.
+@end table
+
+Extra spaces are allowed and ignored at the beginning of the conditional
+directive line, but a tab is not allowed.  (If the line begins with a tab,
+it will be considered a command for a rule.)  Aside from this, extra spaces
+or tabs may be inserted with no effect anywhere except within the directive
+name or within an argument.  A comment starting with @samp{#} may appear at
+the end of the line.
+
+The other two directives that play a part in a conditional are @code{else}
+and @code{endif}.  Each of these directives is written as one word, with no
+arguments.  Extra spaces are allowed and ignored at the beginning of the
+line, and spaces or tabs at the end.  A comment starting with @samp{#} may
+appear at the end of the line.
+
+Conditionals affect which lines of the makefile @code{make} uses.  If
+the condition is true, @code{make} reads the lines of the
+@var{text-if-true} as part of the makefile; if the condition is false,
+@code{make} ignores those lines completely.  It follows that syntactic
+units of the makefile, such as rules, may safely be split across the
+beginning or the end of the conditional.@refill
+
+@code{make} evaluates conditionals when it reads a makefile.
+Consequently, you cannot use automatic variables in the tests of
+conditionals because they are not defined until commands are run
+(@pxref{Automatic, , Automatic Variables}).
+
+To prevent intolerable confusion, it is not permitted to start a
+conditional in one makefile and end it in another.  However, you may
+write an @code{include} directive within a conditional, provided you do
+not attempt to terminate the conditional inside the included file.
+
+@node Testing Flags,  , Conditional Syntax, Conditionals
+@section Conditionals that Test Flags
+
+You can write a conditional that tests @code{make} command flags such as
+@samp{-t} by using the variable @code{MAKEFLAGS} together with the
+@code{findstring} function
+(@pxref{Text Functions, , Functions for String Substitution and Analysis}).
+This is useful when @code{touch} is not enough to make a file appear up
+to date.
+
+The @code{findstring} function determines whether one string appears as a
+substring of another.  If you want to test for the @samp{-t} flag,
+use @samp{t} as the first string and the value of @code{MAKEFLAGS} as
+the other.
+
+For example, here is how to arrange to use @samp{ranlib -t} to finish
+marking an archive file up to date:
+
+@example
+archive.a: @dots{}
+ifneq (,$(findstring t,$(MAKEFLAGS)))
+        +touch archive.a
+        +ranlib -t archive.a
+else
+        ranlib archive.a
+endif
+@end example
+
+@noindent
+The @samp{+} prefix marks those command lines as ``recursive'' so
+that they will be executed despite use of the @samp{-t} flag.
+@xref{Recursion, ,Recursive Use of @code{make}}.
+
+@node Functions, Running, Conditionals, Top
+@chapter Functions for Transforming Text
+@cindex functions
+
+@dfn{Functions} allow you to do text processing in the makefile to compute
+the files to operate on or the commands to use.  You use a function in a
+@dfn{function call}, where you give the name of the function and some text
+(the @dfn{arguments}) for the function to operate on.  The result of the
+function's processing is substituted into the makefile at the point of the
+call, just as a variable might be substituted.
+
+@menu
+* Syntax of Functions::         How to write a function call.
+* Text Functions::              General-purpose text manipulation functions.
+* File Name Functions::         Functions for manipulating file names.
+* Foreach Function::            Repeat some text with controlled variation.
+* If Function::                 Conditionally expand a value.
+* Call Function::               Expand a user-defined function.
+* Value Function::              Return the un-expanded value of a variable.
+* Eval Function::               Evaluate the arguments as makefile syntax.
+* Origin Function::             Find where a variable got its value.
+* Shell Function::              Substitute the output of a shell command.
+* Make Control Functions::      Functions that control how make runs.
+@end menu
+
+@node Syntax of Functions, Text Functions, Functions, Functions
+@section Function Call Syntax
+@cindex @code{$}, in function call
+@cindex dollar sign (@code{$}), in function call
+@cindex arguments of functions
+@cindex functions, syntax of
+
+A function call resembles a variable reference.  It looks like this:
+
+@example
+$(@var{function} @var{arguments})
+@end example
+
+@noindent
+or like this:
+
+@example
+$@{@var{function} @var{arguments}@}
+@end example
+
+Here @var{function} is a function name; one of a short list of names
+that are part of @code{make}.  You can also essentially create your own
+functions by using the @code{call} builtin function.
+
+The @var{arguments} are the arguments of the function.  They are
+separated from the function name by one or more spaces or tabs, and if
+there is more than one argument, then they are separated by commas.
+Such whitespace and commas are not part of an argument's value.  The
+delimiters which you use to surround the function call, whether
+parentheses or braces, can appear in an argument only in matching pairs;
+the other kind of delimiters may appear singly.  If the arguments
+themselves contain other function calls or variable references, it is
+wisest to use the same kind of delimiters for all the references; write
+@w{@samp{$(subst a,b,$(x))}}, not @w{@samp{$(subst a,b,$@{x@})}}.  This
+is because it is clearer, and because only one type of delimiter is
+matched to find the end of the reference.
+
+The text written for each argument is processed by substitution of
+variables and function calls to produce the argument value, which
+is the text on which the function acts.  The substitution is done in the
+order in which the arguments appear.
+
+Commas and unmatched parentheses or braces cannot appear in the text of an
+argument as written; leading spaces cannot appear in the text of the first
+argument as written.  These characters can be put into the argument value
+by variable substitution.  First define variables @code{comma} and
+@code{space} whose values are isolated comma and space characters, then
+substitute these variables where such characters are wanted, like this:
+
+@example
+@group
+comma:= ,
+empty:=
+space:= $(empty) $(empty)
+foo:= a b c
+bar:= $(subst $(space),$(comma),$(foo))
+# @r{bar is now `a,b,c'.}
+@end group
+@end example
+
+@noindent
+Here the @code{subst} function replaces each space with a comma, through
+the value of @code{foo}, and substitutes the result.
+
+@node Text Functions, File Name Functions, Syntax of Functions, Functions
+@section Functions for String Substitution and Analysis
+@cindex functions, for text
+
+Here are some functions that operate on strings:
+
+@table @code
+@item $(subst @var{from},@var{to},@var{text})
+@findex subst
+Performs a textual replacement on the text @var{text}: each occurrence
+of @var{from} is replaced by @var{to}.  The result is substituted for
+the function call.  For example,
+
+@example
+$(subst ee,EE,feet on the street)
+@end example
+
+substitutes the string @samp{fEEt on the strEEt}.
+
+@item $(patsubst @var{pattern},@var{replacement},@var{text})
+@findex patsubst
+Finds whitespace-separated words in @var{text} that match
+@var{pattern} and replaces them with @var{replacement}.  Here
+@var{pattern} may contain a @samp{%} which acts as a wildcard,
+matching any number of any characters within a word.  If
+@var{replacement} also contains a @samp{%}, the @samp{%} is replaced
+by the text that matched the @samp{%} in @var{pattern}.  Only the first
+@samp{%} in the @var{pattern} and @var{replacement} is treated this
+way; any subsequent @samp{%} is unchanged.@refill
+
+@cindex @code{%}, quoting in @code{patsubst}
+@cindex @code{%}, quoting with @code{\} (backslash)
+@cindex @code{\} (backslash), to quote @code{%}
+@cindex backslash (@code{\}), to quote @code{%}
+@cindex quoting @code{%}, in @code{patsubst}
+@samp{%} characters in @code{patsubst} function invocations can be
+quoted with preceding backslashes (@samp{\}).  Backslashes that would
+otherwise quote @samp{%} characters can be quoted with more backslashes.
+Backslashes that quote @samp{%} characters or other backslashes are
+removed from the pattern before it is compared file names or has a stem
+substituted into it.  Backslashes that are not in danger of quoting
+@samp{%} characters go unmolested.  For example, the pattern
+@file{the\%weird\\%pattern\\} has @samp{the%weird\} preceding the
+operative @samp{%} character, and @samp{pattern\\} following it.  The
+final two backslashes are left alone because they cannot affect any
+@samp{%} character.@refill
+
+Whitespace between words is folded into single space characters;
+leading and trailing whitespace is discarded.
+
+For example,
+
+@example
+$(patsubst %.c,%.o,x.c.c bar.c)
+@end example
+
+@noindent
+produces the value @samp{x.c.o bar.o}.
+
+Substitution references (@pxref{Substitution Refs, ,Substitution
+References}) are a simpler way to get the effect of the @code{patsubst}
+function:
+
+@example
+$(@var{var}:@var{pattern}=@var{replacement})
+@end example
+
+@noindent
+is equivalent to
+
+@example
+$(patsubst @var{pattern},@var{replacement},$(@var{var}))
+@end example
+
+The second shorthand simplifies one of the most common uses of
+@code{patsubst}: replacing the suffix at the end of file names.
+
+@example
+$(@var{var}:@var{suffix}=@var{replacement})
+@end example
+
+@noindent
+is equivalent to
+
+@example
+$(patsubst %@var{suffix},%@var{replacement},$(@var{var}))
+@end example
+
+@noindent
+For example, you might have a list of object files:
+
+@example
+objects = foo.o bar.o baz.o
+@end example
+
+@noindent
+To get the list of corresponding source files, you could simply write:
+
+@example
+$(objects:.o=.c)
+@end example
+
+@noindent
+instead of using the general form:
+
+@example
+$(patsubst %.o,%.c,$(objects))
+@end example
+
+@item $(strip @var{string})
+@cindex stripping whitespace
+@cindex whitespace, stripping
+@cindex spaces, stripping
+@findex strip
+Removes leading and trailing whitespace from @var{string} and replaces
+each internal sequence of one or more whitespace characters with a
+single space.  Thus, @samp{$(strip a b  c )} results in @w{@samp{a b c}}.
+
+The function @code{strip} can be very useful when used in conjunction
+with conditionals.  When comparing something with the empty string
+@samp{} using @code{ifeq} or @code{ifneq}, you usually want a string of
+just whitespace to match the empty string (@pxref{Conditionals}).
+
+Thus, the following may fail to have the desired results:
+
+@example
+.PHONY: all
+ifneq   "$(needs_made)" ""
+all: $(needs_made)
+else
+all:;@@echo 'Nothing to make!'
+endif
+@end example
+
+@noindent
+Replacing the variable reference @w{@samp{$(needs_made)}} with the
+function call @w{@samp{$(strip $(needs_made))}} in the @code{ifneq}
+directive would make it more robust.@refill
+
+@item $(findstring @var{find},@var{in})
+@findex findstring
+@cindex searching for strings
+@cindex finding strings
+@cindex strings, searching for
+Searches @var{in} for an occurrence of @var{find}.  If it occurs, the
+value is @var{find}; otherwise, the value is empty.  You can use this
+function in a conditional to test for the presence of a specific
+substring in a given string.  Thus, the two examples,
+
+@example
+$(findstring a,a b c)
+$(findstring a,b c)
+@end example
+
+@noindent
+produce the values @samp{a} and @samp{} (the empty string),
+respectively.  @xref{Testing Flags}, for a practical application of
+@code{findstring}.@refill
+
+@need 750
+@findex filter
+@cindex filtering words
+@cindex words, filtering
+@item $(filter @var{pattern}@dots{},@var{text})
+Returns all whitespace-separated words in @var{text} that @emph{do} match
+any of the @var{pattern} words, removing any words that @emph{do not}
+match.  The patterns are written using @samp{%}, just like the patterns
+used in the @code{patsubst} function above.@refill
+
+The @code{filter} function can be used to separate out different types
+of strings (such as file names) in a variable.  For example:
+
+@example
+sources := foo.c bar.c baz.s ugh.h
+foo: $(sources)
+        cc $(filter %.c %.s,$(sources)) -o foo
+@end example
+
+@noindent
+says that @file{foo} depends of @file{foo.c}, @file{bar.c},
+@file{baz.s} and @file{ugh.h} but only @file{foo.c}, @file{bar.c} and
+@file{baz.s} should be specified in the command to the
+compiler.@refill
+
+@item $(filter-out @var{pattern}@dots{},@var{text})
+@findex filter-out
+@cindex filtering out words
+@cindex words, filtering out
+Returns all whitespace-separated words in @var{text} that @emph{do not}
+match any of the @var{pattern} words, removing the words that @emph{do}
+match one or more.  This is the exact opposite of the @code{filter}
+function.@refill
+
+For example, given:
+
+@example
+@group
+objects=main1.o foo.o main2.o bar.o
+mains=main1.o main2.o
+@end group
+@end example
+
+@noindent
+the following generates a list which contains all the object files not
+in @samp{mains}:
+
+@example
+$(filter-out $(mains),$(objects))
+@end example
+
+@need 1500
+@findex sort
+@cindex sorting words
+@item $(sort @var{list})
+Sorts the words of @var{list} in lexical order, removing duplicate
+words.  The output is a list of words separated by single spaces.
+Thus,
+
+@example
+$(sort foo bar lose)
+@end example
+
+@noindent
+returns the value @samp{bar foo lose}.
+
+@cindex removing duplicate words
+@cindex duplicate words, removing
+@cindex words, removing duplicates
+Incidentally, since @code{sort} removes duplicate words, you can use
+it for this purpose even if you don't care about the sort order.
+
+@item $(word @var{n},@var{text})
+@findex word
+@cindex word, selecting a
+@cindex selecting a word
+Returns the @var{n}th word of @var{text}.  The legitimate values of
+@var{n} start from 1.  If @var{n} is bigger than the number of words
+in @var{text}, the value is empty.  For example,
+
+@example
+$(word 2, foo bar baz)
+@end example
+
+@noindent
+returns @samp{bar}.
+
+@item $(wordlist @var{s},@var{e},@var{text})
+@findex wordlist
+@cindex words, selecting lists of
+@cindex selecting word lists
+Returns the list of words in @var{text} starting with word @var{s} and
+ending with word @var{e} (inclusive).  The legitimate values of @var{s}
+and @var{e} start from 1.  If @var{s} is bigger than the number of words
+in @var{text}, the value is empty.  If @var{e} is bigger than the number
+of words in @var{text}, words up to the end of @var{text} are returned.
+If @var{s} is greater than @var{e}, nothing is returned.  For example,
+
+@example
+$(wordlist 2, 3, foo bar baz)
+@end example
+
+@noindent
+returns @samp{bar baz}.
+
+@c Following item phrased to prevent overfull hbox.  --RJC 17 Jul 92
+@item $(words @var{text})
+@findex words
+@cindex words, finding number
+Returns the number of words in @var{text}.
+Thus, the last word of @var{text} is
+@w{@code{$(word $(words @var{text}),@var{text})}}.@refill
+
+@item $(firstword @var{names}@dots{})
+@findex firstword
+@cindex words, extracting first
+The argument @var{names} is regarded as a series of names, separated
+by whitespace.  The value is the first name in the series.  The rest
+of the names are ignored.
+
+For example,
+
+@example
+$(firstword foo bar)
+@end example
+
+@noindent
+produces the result @samp{foo}.  Although @code{$(firstword
+@var{text})} is the same as @code{$(word 1,@var{text})}, the
+@code{firstword} function is retained for its simplicity.@refill
+@end table
+
+Here is a realistic example of the use of @code{subst} and
+@code{patsubst}.  Suppose that a makefile uses the @code{VPATH} variable
+to specify a list of directories that @code{make} should search for
+prerequisite files
+(@pxref{General Search, , @code{VPATH} Search Path for All Prerequisites}).
+This example shows how to
+tell the C compiler to search for header files in the same list of
+directories.@refill
+
+The value of @code{VPATH} is a list of directories separated by colons,
+such as @samp{src:../headers}.  First, the @code{subst} function is used to
+change the colons to spaces:
+
+@example
+$(subst :, ,$(VPATH))
+@end example
+
+@noindent
+This produces @samp{src ../headers}.  Then @code{patsubst} is used to turn
+each directory name into a @samp{-I} flag.  These can be added to the
+value of the variable @code{CFLAGS}, which is passed automatically to the C
+compiler, like this:
+
+@example
+override CFLAGS += $(patsubst %,-I%,$(subst :, ,$(VPATH)))
+@end example
+
+@noindent
+The effect is to append the text @samp{-Isrc -I../headers} to the
+previously given value of @code{CFLAGS}.  The @code{override} directive is
+used so that the new value is assigned even if the previous value of
+@code{CFLAGS} was specified with a command argument (@pxref{Override
+Directive, , The @code{override} Directive}).
+
+@node File Name Functions, Foreach Function, Text Functions, Functions
+@section Functions for File Names
+@cindex functions, for file names
+@cindex file name functions
+
+Several of the built-in expansion functions relate specifically to
+taking apart file names or lists of file names.
+
+Each of the following functions performs a specific transformation on a
+file name.  The argument of the function is regarded as a series of file
+names, separated by whitespace.  (Leading and trailing whitespace is
+ignored.)  Each file name in the series is transformed in the same way and
+the results are concatenated with single spaces between them.
+
+@table @code
+@item $(dir @var{names}@dots{})
+@findex dir
+@cindex directory part
+@cindex file name, directory part
+Extracts the directory-part of each file name in @var{names}.  The
+directory-part of the file name is everything up through (and
+including) the last slash in it.  If the file name contains no slash,
+the directory part is the string @samp{./}.  For example,
+
+@example
+$(dir src/foo.c hacks)
+@end example
+
+@noindent
+produces the result @samp{src/ ./}.
+
+@item $(notdir @var{names}@dots{})
+@findex notdir
+@cindex file name, nondirectory part
+@cindex nondirectory part
+Extracts all but the directory-part of each file name in @var{names}.
+If the file name contains no slash, it is left unchanged.  Otherwise,
+everything through the last slash is removed from it.
+
+A file name that ends with a slash becomes an empty string.  This is
+unfortunate, because it means that the result does not always have the
+same number of whitespace-separated file names as the argument had;
+but we do not see any other valid alternative.
+
+For example,
+
+@example
+$(notdir src/foo.c hacks)
+@end example
+
+@noindent
+produces the result @samp{foo.c hacks}.
+
+@item $(suffix @var{names}@dots{})
+@findex suffix
+@cindex suffix, function to find
+@cindex file name suffix
+Extracts the suffix of each file name in @var{names}.  If the file name
+contains a period, the suffix is everything starting with the last
+period.  Otherwise, the suffix is the empty string.  This frequently
+means that the result will be empty when @var{names} is not, and if
+@var{names} contains multiple file names, the result may contain fewer
+file names.
+
+For example,
+
+@example
+$(suffix src/foo.c src-1.0/bar.c hacks)
+@end example
+
+@noindent
+produces the result @samp{.c .c}.
+
+@item $(basename @var{names}@dots{})
+@findex basename
+@cindex basename
+@cindex file name, basename of
+Extracts all but the suffix of each file name in @var{names}.  If the
+file name contains a period, the basename is everything starting up to
+(and not including) the last period.  Periods in the directory part are
+ignored.  If there is no period, the basename is the entire file name.
+For example,
+
+@example
+$(basename src/foo.c src-1.0/bar hacks)
+@end example
+
+@noindent
+produces the result @samp{src/foo src-1.0/bar hacks}.
+
+@c plural convention with dots (be consistent)
+@item $(addsuffix @var{suffix},@var{names}@dots{})
+@findex addsuffix
+@cindex suffix, adding
+@cindex file name suffix, adding
+The argument @var{names} is regarded as a series of names, separated
+by whitespace; @var{suffix} is used as a unit.  The value of
+@var{suffix} is appended to the end of each individual name and the
+resulting larger names are concatenated with single spaces between
+them.  For example,
+
+@example
+$(addsuffix .c,foo bar)
+@end example
+
+@noindent
+produces the result @samp{foo.c bar.c}.
+
+@item $(addprefix @var{prefix},@var{names}@dots{})
+@findex addprefix
+@cindex prefix, adding
+@cindex file name prefix, adding
+The argument @var{names} is regarded as a series of names, separated
+by whitespace; @var{prefix} is used as a unit.  The value of
+@var{prefix} is prepended to the front of each individual name and the
+resulting larger names are concatenated with single spaces between
+them.  For example,
+
+@example
+$(addprefix src/,foo bar)
+@end example
+
+@noindent
+produces the result @samp{src/foo src/bar}.
+
+@item $(join @var{list1},@var{list2})
+@findex join
+@cindex joining lists of words
+@cindex words, joining lists
+Concatenates the two arguments word by word: the two first words (one
+from each argument) concatenated form the first word of the result, the
+two second words form the second word of the result, and so on.  So the
+@var{n}th word of the result comes from the @var{n}th word of each
+argument.  If one argument has more words that the other, the extra
+words are copied unchanged into the result.
+
+For example, @samp{$(join a b,.c .o)} produces @samp{a.c b.o}.
+
+Whitespace between the words in the lists is not preserved; it is
+replaced with a single space.
+
+This function can merge the results of the @code{dir} and
+@code{notdir} functions, to produce the original list of files which
+was given to those two functions.@refill
+
+@item $(wildcard @var{pattern})
+@findex wildcard
+@cindex wildcard, function
+The argument @var{pattern} is a file name pattern, typically containing
+wildcard characters (as in shell file name patterns).  The result of
+@code{wildcard} is a space-separated list of the names of existing files
+that match the pattern.
+@xref{Wildcards, ,Using Wildcard Characters in File Names}.
+@end table
+
+@node Foreach Function, If Function, File Name Functions, Functions
+@section The @code{foreach} Function
+@findex foreach
+@cindex words, iterating over
+
+The @code{foreach} function is very different from other functions.  It
+causes one piece of text to be used repeatedly, each time with a different
+substitution performed on it.  It resembles the @code{for} command in the
+shell @code{sh} and the @code{foreach} command in the C-shell @code{csh}.
+
+The syntax of the @code{foreach} function is:
+
+@example
+$(foreach @var{var},@var{list},@var{text})
+@end example
+
+@noindent
+The first two arguments, @var{var} and @var{list}, are expanded before
+anything else is done; note that the last argument, @var{text}, is
+@strong{not} expanded at the same time.  Then for each word of the expanded
+value of @var{list}, the variable named by the expanded value of @var{var}
+is set to that word, and @var{text} is expanded.  Presumably @var{text}
+contains references to that variable, so its expansion will be different
+each time.
+
+The result is that @var{text} is expanded as many times as there are
+whitespace-separated words in @var{list}.  The multiple expansions of
+@var{text} are concatenated, with spaces between them, to make the result
+of @code{foreach}.
+
+This simple example sets the variable @samp{files} to the list of all files
+in the directories in the list @samp{dirs}:
+
+@example
+dirs := a b c d
+files := $(foreach dir,$(dirs),$(wildcard $(dir)/*))
+@end example
+
+Here @var{text} is @samp{$(wildcard $(dir)/*)}.  The first repetition
+finds the value @samp{a} for @code{dir}, so it produces the same result
+as @samp{$(wildcard a/*)}; the second repetition produces the result
+of @samp{$(wildcard b/*)}; and the third, that of @samp{$(wildcard c/*)}.
+
+This example has the same result (except for setting @samp{dirs}) as
+the following example:
+
+@example
+files := $(wildcard a/* b/* c/* d/*)
+@end example
+
+When @var{text} is complicated, you can improve readability by giving it
+a name, with an additional variable:
+
+@example
+find_files = $(wildcard $(dir)/*)
+dirs := a b c d
+files := $(foreach dir,$(dirs),$(find_files))
+@end example
+
+@noindent
+Here we use the variable @code{find_files} this way.  We use plain @samp{=}
+to define a recursively-expanding variable, so that its value contains an
+actual function call to be reexpanded under the control of @code{foreach};
+a simply-expanded variable would not do, since @code{wildcard} would be
+called only once at the time of defining @code{find_files}.
+
+The @code{foreach} function has no permanent effect on the variable
+@var{var}; its value and flavor after the @code{foreach} function call are
+the same as they were beforehand.  The other values which are taken from
+@var{list} are in effect only temporarily, during the execution of
+@code{foreach}.  The variable @var{var} is a simply-expanded variable
+during the execution of @code{foreach}.  If @var{var} was undefined
+before the @code{foreach} function call, it is undefined after the call.
+@xref{Flavors, ,The Two Flavors of Variables}.@refill
+
+You must take care when using complex variable expressions that result in
+variable names because many strange things are valid variable names, but
+are probably not what you intended.  For example,
+
+@smallexample
+files := $(foreach Esta escrito en espanol!,b c ch,$(find_files))
+@end smallexample
+
+@noindent
+might be useful if the value of @code{find_files} references the variable
+whose name is @samp{Esta escrito en espanol!} (es un nombre bastante largo,
+no?), but it is more likely to be a mistake.
+
+@node If Function, Call Function, Foreach Function, Functions
+@section The @code{if} Function
+@findex if
+@cindex conditional expansion
+
+The @code{if} function provides support for conditional expansion in a
+functional context (as opposed to the GNU @code{make} makefile
+conditionals such as @code{ifeq} (@pxref{Conditional Syntax, ,Syntax of
+Conditionals}).
+
+An @code{if} function call can contain either two or three arguments:
+
+@example
+$(if @var{condition},@var{then-part}[,@var{else-part}])
+@end example
+
+The first argument, @var{condition}, first has all preceding and
+trailing whitespace stripped, then is expanded.  If it expands to any
+non-empty string, then the condition is considered to be true.  If it
+expands to an empty string, the condition is considered to be false.
+
+If the condition is true then the second argument, @var{then-part}, is
+evaluated and this is used as the result of the evaluation of the entire
+@code{if} function.
+
+If the condition is false then the third argument, @var{else-part}, is
+evaluated and this is the result of the @code{if} function.  If there is
+no third argument, the @code{if} function evaluates to nothing (the
+empty string).
+
+Note that only one of the @var{then-part} or the @var{else-part} will be
+evaluated, never both.  Thus, either can contain side-effects (such as
+@code{shell} function calls, etc.)
+
+@node Call Function, Value Function, If Function, Functions
+@section The @code{call} Function
+@findex call
+@cindex functions, user defined
+@cindex user defined functions
+
+The @code{call} function is unique in that it can be used to create new
+parameterized functions.  You can write a complex expression as the
+value of a variable, then use @code{call} to expand it with different
+values.
+
+The syntax of the @code{call} function is:
+
+@example
+$(call @var{variable},@var{param},@var{param},@dots{})
+@end example
+
+When @code{make} expands this function, it assigns each @var{param} to
+temporary variables @code{$(1)}, @code{$(2)}, etc.  The variable
+@code{$(0)} will contain @var{variable}.  There is no maximum number of
+parameter arguments.  There is no minimum, either, but it doesn't make
+sense to use @code{call} with no parameters.
+
+Then @var{variable} is expanded as a @code{make} variable in the context
+of these temporary assignments.  Thus, any reference to @code{$(1)} in
+the value of @var{variable} will resolve to the first @var{param} in the
+invocation of @code{call}.
+
+Note that @var{variable} is the @emph{name} of a variable, not a
+@emph{reference} to that variable.  Therefore you would not normally use
+a @samp{$} or parentheses when writing it.  (You can, however, use a
+variable reference in the name if you want the name not to be a
+constant.)
+
+If @var{variable} is the name of a builtin function, the builtin function
+is always invoked (even if a @code{make} variable by that name also
+exists).
+
+The @code{call} function expands the @var{param} arguments before
+assigning them to temporary variables.  This means that @var{variable}
+values containing references to builtin functions that have special
+expansion rules, like @code{foreach} or @code{if}, may not work as you
+expect.
+
+Some examples may make this clearer.
+
+This macro simply reverses its arguments:
+
+@smallexample
+reverse = $(2) $(1)
+
+foo = $(call reverse,a,b)
+@end smallexample
+
+@noindent
+Here @var{foo} will contain @samp{b a}.
+
+This one is slightly more interesting: it defines a macro to search for
+the first instance of a program in @code{PATH}:
+
+@smallexample
+pathsearch = $(firstword $(wildcard $(addsuffix /$(1),$(subst :, ,$(PATH)))))
+
+LS := $(call pathsearch,ls)
+@end smallexample
+
+@noindent
+Now the variable LS contains @code{/bin/ls} or similar.
+
+The @code{call} function can be nested.  Each recursive invocation gets
+its own local values for @code{$(1)}, etc. that mask the values of
+higher-level @code{call}.  For example, here is an implementation of a
+@dfn{map} function:
+
+@smallexample
+map = $(foreach a,$(2),$(call $(1),$(a)))
+@end smallexample
+
+Now you can @var{map} a function that normally takes only one argument,
+such as @code{origin}, to multiple values in one step:
+
+@smallexample
+o = $(call map,origin,o map MAKE)
+@end smallexample
+
+and end up with @var{o} containing something like @samp{file file default}.
+
+A final caution: be careful when adding whitespace to the arguments to
+@code{call}.  As with other functions, any whitespace contained in the
+second and subsequent arguments is kept; this can cause strange
+effects.  It's generally safest to remove all extraneous whitespace when
+providing parameters to @code{call}.
+
+@node Value Function, Eval Function, Call Function, Functions
+@comment  node-name,  next,  previous,  up
+@section The @code{value} Function
+@findex value
+@cindex variables, unexpanded value
+
+The @code{value} function provides a way for you to use the value of a
+variable @emph{without} having it expanded.  Please note that this
+does not undo expansions which have already occurred; for example if
+you create a simply expanded variable its value is expanded during the
+definition; in that case the @code{value} function will return the
+same result as using the variable directly.
+
+The syntax of the @code{value} function is:
+
+@example
+$(value @var{variable})
+@end example
+
+Note that @var{variable} is the @emph{name} of a variable; not a
+@emph{reference} to that variable.  Therefore you would not normally
+use a @samp{$} or parentheses when writing it.  (You can, however, use
+a variable reference in the name if you want the name not to be a
+constant.)
+
+The result of this function is a string containing the value of
+@var{variable}, without any expansion occurring.  For example, in this
+makefile:
+
+@example
+@group
+FOO = $PATH
+
+all:
+        @@echo $(FOO)
+        @@echo $(value FOO)
+@end group
+@end example
+
+@noindent
+The first output line would be @code{ATH}, since the ``$P'' would be
+expanded as a @code{make} variable, while the second output line would
+be the current value of your @code{$PATH} environment variable, since
+the @code{value} function avoided the expansion.
+
+The @code{value} function is most often used in conjunction with the
+@code{eval} function (@pxref{Eval Function}).
+
+@node Eval Function, Origin Function, Value Function, Functions
+@comment  node-name,  next,  previous,  up
+@section The @code{eval} Function
+@findex eval
+@cindex evaluating makefile syntax
+@cindex makefile syntax, evaluating
+
+The @code{eval} function is very special: it allows you to define new
+makefile constructs that are not constant; which are the result of
+evaluating other variables and functions.  The argument to the
+@code{eval} function is expanded, then the results of that expansion
+are parsed as makefile syntax.  The expanded results can define new
+@code{make} variables, targets, implicit or explicit rules, etc.
+
+The result of the @code{eval} function is always the empty string;
+thus, it can be placed virtually anywhere in a makefile without
+causing syntax errors.
+
+It's important to realize that the @code{eval} argument is expanded
+@emph{twice}; first by the @code{eval} function, then the results of
+that expansion are expanded again when they are parsed as makefile
+syntax.  This means you may need to provide extra levels of escaping
+for ``$'' characters when using @code{eval}.  The @code{value}
+function (@pxref{Value Function}) can sometimes be useful in these
+situations, to circumvent unwanted expansions.
+
+Here is an example of how @code{eval} can be used; this example
+combines a number of concepts and other functions.  Although it might
+seem overly complex to use @code{eval} in this example, rather than
+just writing out the rules, consider two things: first, the template
+definition (in @code{PROGRAM_template}) could need to be much more
+complex than it is here; and second, you might put the complex,
+``generic'' part of this example into another makefile, then include
+it in all the individual makefiles.  Now your individual makefiles are
+quite straightforward.
+
+@example
+@group
+PROGRAMS    = server client
+
+server_OBJS = server.o server_priv.o server_access.o
+server_LIBS = priv protocol
+
+client_OBJS = client.o client_api.o client_mem.o
+client_LIBS = protocol
+
+# Everything after this is generic
+
+.PHONY: all
+all: $(PROGRAMS)
+
+define PROGRAM_template
+ $(1): $$($(1)_OBJ) $$($(1)_LIBS:%=-l%)
+ ALL_OBJS   += $$($(1)_OBJS)
+endef
+
+$(foreach prog,$(PROGRAMS),$(eval $(call PROGRAM_template,$(prog))))
+
+$(PROGRAMS):
+        $(LINK.o) $^ $(LDLIBS) -o $@@
+
+clean:
+        rm -f $(ALL_OBJS) $(PROGRAMS)
+@end group
+@end example
+
+@node Origin Function, Shell Function, Eval Function, Functions
+@section The @code{origin} Function
+@findex origin
+@cindex variables, origin of
+@cindex origin of variable
+
+The @code{origin} function is unlike most other functions in that it does
+not operate on the values of variables; it tells you something @emph{about}
+a variable.  Specifically, it tells you where it came from.
+
+The syntax of the @code{origin} function is:
+
+@example
+$(origin @var{variable})
+@end example
+
+Note that @var{variable} is the @emph{name} of a variable to inquire about;
+not a @emph{reference} to that variable.  Therefore you would not normally
+use a @samp{$} or parentheses when writing it.  (You can, however, use a
+variable reference in the name if you want the name not to be a constant.)
+
+The result of this function is a string telling you how the variable
+@var{variable} was defined:
+
+@table @samp
+@item undefined
+
+if @var{variable} was never defined.
+
+@item default
+
+if @var{variable} has a default definition, as is usual with @code{CC}
+and so on.  @xref{Implicit Variables, ,Variables Used by Implicit Rules}.
+Note that if you have redefined a default variable, the @code{origin}
+function will return the origin of the later definition.
+
+@item environment
+
+if @var{variable} was defined as an environment variable and the
+@samp{-e} option is @emph{not} turned on (@pxref{Options Summary, ,Summary of Options}).
+
+@item environment override
+
+if @var{variable} was defined as an environment variable and the
+@w{@samp{-e}} option @emph{is} turned on (@pxref{Options Summary,
+,Summary of Options}).@refill
+
+@item file
+
+if @var{variable} was defined in a makefile.
+
+@item command line
+
+if @var{variable} was defined on the command line.
+
+@item override
+
+if @var{variable} was defined with an @code{override} directive in a
+makefile (@pxref{Override Directive, ,The @code{override} Directive}).
+
+@item automatic
+
+if @var{variable} is an automatic variable defined for the
+execution of the commands for each rule
+(@pxref{Automatic, , Automatic Variables}).
+@end table
+
+This information is primarily useful (other than for your curiosity) to
+determine if you want to believe the value of a variable.  For example,
+suppose you have a makefile @file{foo} that includes another makefile
+@file{bar}.  You want a variable @code{bletch} to be defined in @file{bar}
+if you run the command @w{@samp{make -f bar}}, even if the environment contains
+a definition of @code{bletch}.  However, if @file{foo} defined
+@code{bletch} before including @file{bar}, you do not want to override that
+definition.  This could be done by using an @code{override} directive in
+@file{foo}, giving that definition precedence over the later definition in
+@file{bar}; unfortunately, the @code{override} directive would also
+override any command line definitions.  So, @file{bar} could
+include:@refill
+
+@example
+@group
+ifdef bletch
+ifeq "$(origin bletch)" "environment"
+bletch = barf, gag, etc.
+endif
+endif
+@end group
+@end example
+
+@noindent
+If @code{bletch} has been defined from the environment, this will redefine
+it.
+
+If you want to override a previous definition of @code{bletch} if it came
+from the environment, even under @samp{-e}, you could instead write:
+
+@example
+@group
+ifneq "$(findstring environment,$(origin bletch))" ""
+bletch = barf, gag, etc.
+endif
+@end group
+@end example
+
+Here the redefinition takes place if @samp{$(origin bletch)} returns either
+@samp{environment} or @samp{environment override}.
+@xref{Text Functions, , Functions for String Substitution and Analysis}.
+
+@node Shell Function, Make Control Functions, Origin Function, Functions
+@section The @code{shell} Function
+@findex shell
+@cindex commands, expansion
+@cindex backquotes
+@cindex shell command, function for
+
+The @code{shell} function is unlike any other function except the
+@code{wildcard} function
+(@pxref{Wildcard Function, ,The Function @code{wildcard}}) in that it
+communicates with the world outside of @code{make}.
+
+The @code{shell} function performs the same function that backquotes
+(@samp{`}) perform in most shells: it does @dfn{command expansion}.  This
+means that it takes an argument that is a shell command and returns the
+output of the command.  The only processing @code{make} does on the result,
+before substituting it into the surrounding text, is to convert each
+newline or carriage-return / newline pair to a single space.  It also
+removes the trailing (carriage-return and) newline, if it's the last
+thing in the result.@refill
+
+The commands run by calls to the @code{shell} function are run when the
+function calls are expanded.  In most cases, this is when the makefile is
+read in.  The exception is that function calls in the commands of the rules
+are expanded when the commands are run, and this applies to @code{shell}
+function calls like all others.
+
+Here are some examples of the use of the @code{shell} function:
+
+@example
+contents := $(shell cat foo)
+@end example
+
+@noindent
+sets @code{contents} to the contents of the file @file{foo}, with a space
+(rather than a newline) separating each line.
+
+@example
+files := $(shell echo *.c)
+@end example
+
+@noindent
+sets @code{files} to the expansion of @samp{*.c}.  Unless @code{make} is
+using a very strange shell, this has the same result as
+@w{@samp{$(wildcard *.c)}}.@refill
+
+@node Make Control Functions,  , Shell Function, Functions
+@section Functions That Control Make
+@cindex functions, for controlling make
+@cindex controlling make
+
+These functions control the way make runs.  Generally, they are used to
+provide information to the user of the makefile or to cause make to stop
+if some sort of environmental error is detected.
+
+@table @code
+@item $(error @var{text}@dots{})
+@findex error
+@cindex error, stopping on
+@cindex stopping make
+Generates a fatal error where the message is @var{text}.  Note that the
+error is generated whenever this function is evaluated.  So, if you put
+it inside a command script or on the right side of a recursive variable
+assignment, it won't be evaluated until later.  The @var{text} will be
+expanded before the error is generated.
+
+For example,
+
+@example
+ifdef ERROR1
+$(error error is $(ERROR1))
+endif
+@end example
+
+@noindent
+will generate a fatal error during the read of the makefile if the
+@code{make} variable @code{ERROR1} is defined.  Or,
+
+@example
+ERR = $(error found an error!)
+
+.PHONY: err
+err: ; $(ERR)
+@end example
+
+@noindent
+will generate a fatal error while @code{make} is running, if the
+@code{err} target is invoked.
+
+@item $(warning @var{text}@dots{})
+@findex warning
+@cindex warnings, printing
+@cindex printing user warnings
+This function works similarly to the @code{error} function, above,
+except that @code{make} doesn't exit.  Instead, @var{text} is expanded
+and the resulting message is displayed, but processing of the makefile
+continues.
+
+The result of the expansion of this function is the empty string.
+@end table
+
+@node Running, Implicit Rules, Functions, Top
+@chapter How to Run @code{make}
+
+A makefile that says how to recompile a program can be used in more
+than one way.  The simplest use is to recompile every file that is out
+of date.  Usually, makefiles are written so that if you run
+@code{make} with no arguments, it does just that.
+
+But you might want to update only some of the files; you might want to use
+a different compiler or different compiler options; you might want just to
+find out which files are out of date without changing them.
+
+By giving arguments when you run @code{make}, you can do any of these
+things and many others.
+
+The exit status of @code{make} is always one of three values:
+@table @code
+@item 0
+The exit status is zero if @code{make} is successful.
+@item 2
+The exit status is two if @code{make} encounters any errors.
+It will print messages describing the particular errors.
+@item 1
+The exit status is one if you use the @samp{-q} flag and @code{make}
+determines that some target is not already up to date.
+@xref{Instead of Execution, ,Instead of Executing the Commands}.
+@end table
+
+@menu
+* Makefile Arguments::          How to specify which makefile to use.
+* Goals::                       How to use goal arguments to specify which
+                                  parts of the makefile to use.
+* Instead of Execution::        How to use mode flags to specify what
+                                  kind of thing to do with the commands
+                                  in the makefile other than simply
+                                  execute them.
+* Avoiding Compilation::        How to avoid recompiling certain files.
+* Overriding::                  How to override a variable to specify
+                                  an alternate compiler and other things.
+* Testing::                     How to proceed past some errors, to
+                                  test compilation.
+* Options Summary::             Summary of Options
+@end menu
+
+@node Makefile Arguments, Goals, Running, Running
+@section Arguments to Specify the Makefile
+@cindex @code{--file}
+@cindex @code{--makefile}
+@cindex @code{-f}
+
+The way to specify the name of the makefile is with the @samp{-f} or
+@samp{--file} option (@samp{--makefile} also works).  For example,
+@samp{-f altmake} says to use the file @file{altmake} as the makefile.
+
+If you use the @samp{-f} flag several times and follow each @samp{-f}
+with an argument, all the specified files are used jointly as
+makefiles.
+
+If you do not use the @samp{-f} or @samp{--file} flag, the default is
+to try @file{GNUmakefile}, @file{makefile}, and @file{Makefile}, in
+that order, and use the first of these three which exists or can be made
+(@pxref{Makefiles, ,Writing Makefiles}).@refill
+
+@node Goals, Instead of Execution, Makefile Arguments, Running
+@section Arguments to Specify the Goals
+@cindex goal, how to specify
+
+The @dfn{goals} are the targets that @code{make} should strive ultimately
+to update.  Other targets are updated as well if they appear as
+prerequisites of goals, or prerequisites of prerequisites of goals, etc.
+
+By default, the goal is the first target in the makefile (not counting
+targets that start with a period).  Therefore, makefiles are usually
+written so that the first target is for compiling the entire program or
+programs they describe.  If the first rule in the makefile has several
+targets, only the first target in the rule becomes the default goal, not
+the whole list.
+
+You can specify a different goal or goals with arguments to @code{make}.
+Use the name of the goal as an argument.  If you specify several goals,
+@code{make} processes each of them in turn, in the order you name them.
+
+Any target in the makefile may be specified as a goal (unless it
+starts with @samp{-} or contains an @samp{=}, in which case it will be
+parsed as a switch or variable definition, respectively).  Even
+targets not in the makefile may be specified, if @code{make} can find
+implicit rules that say how to make them.
+
+@cindex @code{MAKECMDGOALS}
+@vindex MAKECMDGOALS
+@code{Make} will set the special variable @code{MAKECMDGOALS} to the
+list of goals you specified on the command line.  If no goals were given
+on the command line, this variable is empty.  Note that this variable
+should be used only in special circumstances.
+
+An example of appropriate use is to avoid including @file{.d} files
+during @code{clean} rules (@pxref{Automatic Prerequisites}), so
+@code{make} won't create them only to immediately remove them
+again:@refill
+
+@example
+@group
+sources = foo.c bar.c
+
+ifneq ($(MAKECMDGOALS),clean)
+include $(sources:.c=.d)
+endif
+@end group
+@end example
+
+One use of specifying a goal is if you want to compile only a part of
+the program, or only one of several programs.  Specify as a goal each
+file that you wish to remake.  For example, consider a directory containing
+several programs, with a makefile that starts like this:
+
+@example
+.PHONY: all
+all: size nm ld ar as
+@end example
+
+If you are working on the program @code{size}, you might want to say
+@w{@samp{make size}} so that only the files of that program are recompiled.
+
+Another use of specifying a goal is to make files that are not normally
+made.  For example, there may be a file of debugging output, or a
+version of the program that is compiled specially for testing, which has
+a rule in the makefile but is not a prerequisite of the default goal.
+
+Another use of specifying a goal is to run the commands associated with
+a phony target (@pxref{Phony Targets}) or empty target (@pxref{Empty
+Targets, ,Empty Target Files to Record Events}).  Many makefiles contain
+a phony target named @file{clean} which deletes everything except source
+files.  Naturally, this is done only if you request it explicitly with
+@w{@samp{make clean}}.  Following is a list of typical phony and empty
+target names.  @xref{Standard Targets}, for a detailed list of all the
+standard target names which GNU software packages use.
+
+@table @file
+@item all
+@cindex @code{all} @r{(standard target)}
+Make all the top-level targets the makefile knows about.
+
+@item clean
+@cindex @code{clean} @r{(standard target)}
+Delete all files that are normally created by running @code{make}.
+
+@item mostlyclean
+@cindex @code{mostlyclean} @r{(standard target)}
+Like @samp{clean}, but may refrain from deleting a few files that people
+normally don't want to recompile.  For example, the @samp{mostlyclean}
+target for GCC does not delete @file{libgcc.a}, because recompiling it
+is rarely necessary and takes a lot of time.
+
+@item distclean
+@cindex @code{distclean} @r{(standard target)}
+@itemx realclean
+@cindex @code{realclean} @r{(standard target)}
+@itemx clobber
+@cindex @code{clobber} @r{(standard target)}
+Any of these targets might be defined to delete @emph{more} files than
+@samp{clean} does.  For example, this would delete configuration files
+or links that you would normally create as preparation for compilation,
+even if the makefile itself cannot create these files.
+
+@item install
+@cindex @code{install} @r{(standard target)}
+Copy the executable file into a directory that users typically search
+for commands; copy any auxiliary files that the executable uses into
+the directories where it will look for them.
+
+@item print
+@cindex @code{print} @r{(standard target)}
+Print listings of the source files that have changed.
+
+@item tar
+@cindex @code{tar} @r{(standard target)}
+Create a tar file of the source files.
+
+@item shar
+@cindex @code{shar} @r{(standard target)}
+Create a shell archive (shar file) of the source files.
+
+@item dist
+@cindex @code{dist} @r{(standard target)}
+Create a distribution file of the source files.  This might
+be a tar file, or a shar file, or a compressed version of one of the
+above, or even more than one of the above.
+
+@item TAGS
+@cindex @code{TAGS} @r{(standard target)}
+Update a tags table for this program.
+
+@item check
+@cindex @code{check} @r{(standard target)}
+@itemx test
+@cindex @code{test} @r{(standard target)}
+Perform self tests on the program this makefile builds.
+@end table
+
+@node Instead of Execution, Avoiding Compilation, Goals, Running
+@section Instead of Executing the Commands
+@cindex execution, instead of
+@cindex commands, instead of executing
+
+The makefile tells @code{make} how to tell whether a target is up to date,
+and how to update each target.  But updating the targets is not always
+what you want.  Certain options specify other activities for @code{make}.
+
+@comment Extra blank lines make it print better.
+@table @samp
+@item -n
+@itemx --just-print
+@itemx --dry-run
+@itemx --recon
+@cindex @code{--just-print}
+@cindex @code{--dry-run}
+@cindex @code{--recon}
+@cindex @code{-n}
+
+``No-op''.  The activity is to print what commands would be used to make
+the targets up to date, but not actually execute them.
+
+@item -t
+@itemx --touch
+@cindex @code{--touch}
+@cindex touching files
+@cindex target, touching
+@cindex @code{-t}
+
+``Touch''.  The activity is to mark the targets as up to date without
+actually changing them.  In other words, @code{make} pretends to compile
+the targets but does not really change their contents.
+
+@item -q
+@itemx --question
+@cindex @code{--question}
+@cindex @code{-q}
+@cindex question mode
+
+``Question''.  The activity is to find out silently whether the targets
+are up to date already; but execute no commands in either case.  In other
+words, neither compilation nor output will occur.
+
+@item -W @var{file}
+@itemx --what-if=@var{file}
+@itemx --assume-new=@var{file}
+@itemx --new-file=@var{file}
+@cindex @code{--what-if}
+@cindex @code{-W}
+@cindex @code{--assume-new}
+@cindex @code{--new-file}
+@cindex what if
+@cindex files, assuming new
+
+``What if''.  Each @samp{-W} flag is followed by a file name.  The given
+files' modification times are recorded by @code{make} as being the present
+time, although the actual modification times remain the same.
+You can use the @samp{-W} flag in conjunction with the @samp{-n} flag
+to see what would happen if you were to modify specific files.@refill
+@end table
+
+With the @samp{-n} flag, @code{make} prints the commands that it would
+normally execute but does not execute them.
+
+With the @samp{-t} flag, @code{make} ignores the commands in the rules
+and uses (in effect) the command @code{touch} for each target that needs to
+be remade.  The @code{touch} command is also printed, unless @samp{-s} or
+@code{.SILENT} is used.  For speed, @code{make} does not actually invoke
+the program @code{touch}.  It does the work directly.
+
+With the @samp{-q} flag, @code{make} prints nothing and executes no
+commands, but the exit status code it returns is zero if and only if the
+targets to be considered are already up to date.  If the exit status is
+one, then some updating needs to be done.  If @code{make} encounters an
+error, the exit status is two, so you can distinguish an error from a
+target that is not up to date.
+
+It is an error to use more than one of these three flags in the same
+invocation of @code{make}.
+
+The @samp{-n}, @samp{-t}, and @samp{-q} options do not affect command
+lines that begin with @samp{+} characters or contain the strings
+@samp{$(MAKE)} or @samp{$@{MAKE@}}.  Note that only the line containing
+the @samp{+} character or the strings @samp{$(MAKE)} or @samp{$@{MAKE@}}
+is run regardless of these options.  Other lines in the same rule are
+not run unless they too begin with @samp{+} or contain @samp{$(MAKE)} or
+@samp{$@{MAKE@}} (@xref{MAKE Variable, ,How the @code{MAKE} Variable Works}.)
+
+The @samp{-W} flag provides two features:
+
+@itemize @bullet
+@item
+If you also use the @samp{-n} or @samp{-q} flag, you can see what
+@code{make} would do if you were to modify some files.
+
+@item
+Without the @samp{-n} or @samp{-q} flag, when @code{make} is actually
+executing commands, the @samp{-W} flag can direct @code{make} to act
+as if some files had been modified, without actually modifying the
+files.@refill
+@end itemize
+
+Note that the options @samp{-p} and @samp{-v} allow you to obtain other
+information about @code{make} or about the makefiles in use
+(@pxref{Options Summary, ,Summary of Options}).@refill
+
+@node Avoiding Compilation, Overriding, Instead of Execution, Running
+@section Avoiding Recompilation of Some Files
+@cindex @code{-o}
+@cindex @code{--old-file}
+@cindex @code{--assume-old}
+@cindex files, assuming old
+@cindex files, avoiding recompilation of
+@cindex recompilation, avoiding
+
+Sometimes you may have changed a source file but you do not want to
+recompile all the files that depend on it.  For example, suppose you add
+a macro or a declaration to a header file that many other files depend
+on.  Being conservative, @code{make} assumes that any change in the
+header file requires recompilation of all dependent files, but you know
+that they do not need to be recompiled and you would rather not waste
+the time waiting for them to compile.
+
+If you anticipate the problem before changing the header file, you can
+use the @samp{-t} flag.  This flag tells @code{make} not to run the
+commands in the rules, but rather to mark the target up to date by
+changing its last-modification date.  You would follow this procedure:
+
+@enumerate
+@item
+Use the command @samp{make} to recompile the source files that really
+need recompilation, ensuring that the object files are up-to-date
+before you begin.
+
+@item
+Make the changes in the header files.
+
+@item
+Use the command @samp{make -t} to mark all the object files as
+up to date.  The next time you run @code{make}, the changes in the
+header files will not cause any recompilation.
+@end enumerate
+
+If you have already changed the header file at a time when some files
+do need recompilation, it is too late to do this.  Instead, you can
+use the @w{@samp{-o @var{file}}} flag, which marks a specified file as
+``old'' (@pxref{Options Summary, ,Summary of Options}).  This means
+that the file itself will not be remade, and nothing else will be
+remade on its account.  Follow this procedure:
+
+@enumerate
+@item
+Recompile the source files that need compilation for reasons independent
+of the particular header file, with @samp{make -o @var{headerfile}}.
+If several header files are involved, use a separate @samp{-o} option
+for each header file.
+
+@item
+Touch all the object files with @samp{make -t}.
+@end enumerate
+
+@node Overriding, Testing, Avoiding Compilation, Running
+@section Overriding Variables
+@cindex overriding variables with arguments
+@cindex variables, overriding with arguments
+@cindex command line variables
+@cindex variables, command line
+
+An argument that contains @samp{=} specifies the value of a variable:
+@samp{@var{v}=@var{x}} sets the value of the variable @var{v} to @var{x}.
+If you specify a value in this way, all ordinary assignments of the same
+variable in the makefile are ignored; we say they have been
+@dfn{overridden} by the command line argument.
+
+The most common way to use this facility is to pass extra flags to
+compilers.  For example, in a properly written makefile, the variable
+@code{CFLAGS} is included in each command that runs the C compiler, so a
+file @file{foo.c} would be compiled something like this:
+
+@example
+cc -c $(CFLAGS) foo.c
+@end example
+
+Thus, whatever value you set for @code{CFLAGS} affects each compilation
+that occurs.  The makefile probably specifies the usual value for
+@code{CFLAGS}, like this:
+
+@example
+CFLAGS=-g
+@end example
+
+Each time you run @code{make}, you can override this value if you
+wish.  For example, if you say @samp{make CFLAGS='-g -O'}, each C
+compilation will be done with @samp{cc -c -g -O}.  (This also
+illustrates how you can use quoting in the shell to enclose spaces and
+other special characters in the value of a variable when you override
+it.)
+
+The variable @code{CFLAGS} is only one of many standard variables that
+exist just so that you can change them this way.  @xref{Implicit
+Variables, , Variables Used by Implicit Rules}, for a complete list.
+
+You can also program the makefile to look at additional variables of your
+own, giving the user the ability to control other aspects of how the
+makefile works by changing the variables.
+
+When you override a variable with a command argument, you can define either
+a recursively-expanded variable or a simply-expanded variable.  The
+examples shown above make a recursively-expanded variable; to make a
+simply-expanded variable, write @samp{:=} instead of @samp{=}.  But, unless
+you want to include a variable reference or function call in the
+@emph{value} that you specify, it makes no difference which kind of
+variable you create.
+
+There is one way that the makefile can change a variable that you have
+overridden.  This is to use the @code{override} directive, which is a line
+that looks like this: @samp{override @var{variable} = @var{value}}
+(@pxref{Override Directive, ,The @code{override} Directive}).
+
+@node Testing, Options Summary, Overriding, Running
+@section Testing the Compilation of a Program
+@cindex testing compilation
+@cindex compilation, testing
+
+Normally, when an error happens in executing a shell command, @code{make}
+gives up immediately, returning a nonzero status.  No further commands are
+executed for any target.  The error implies that the goal cannot be
+correctly remade, and @code{make} reports this as soon as it knows.
+
+When you are compiling a program that you have just changed, this is not
+what you want.  Instead, you would rather that @code{make} try compiling
+every file that can be tried, to show you as many compilation errors
+as possible.
+
+@cindex @code{-k}
+@cindex @code{--keep-going}
+On these occasions, you should use the @samp{-k} or
+@samp{--keep-going} flag.  This tells @code{make} to continue to
+consider the other prerequisites of the pending targets, remaking them
+if necessary, before it gives up and returns nonzero status.  For
+example, after an error in compiling one object file, @samp{make -k}
+will continue compiling other object files even though it already
+knows that linking them will be impossible.  In addition to continuing
+after failed shell commands, @samp{make -k} will continue as much as
+possible after discovering that it does not know how to make a target
+or prerequisite file.  This will always cause an error message, but
+without @samp{-k}, it is a fatal error (@pxref{Options Summary,
+,Summary of Options}).@refill
+
+The usual behavior of @code{make} assumes that your purpose is to get the
+goals up to date; once @code{make} learns that this is impossible, it might
+as well report the failure immediately.  The @samp{-k} flag says that the
+real purpose is to test as much as possible of the changes made in the
+program, perhaps to find several independent problems so that you can
+correct them all before the next attempt to compile.  This is why Emacs'
+@kbd{M-x compile} command passes the @samp{-k} flag by default.
+
+@node Options Summary,  , Testing, Running
+@section Summary of Options
+@cindex options
+@cindex flags
+@cindex switches
+
+Here is a table of all the options @code{make} understands:
+
+@table @samp
+@item -b
+@cindex @code{-b}
+@itemx -m
+@cindex @code{-m}
+These options are ignored for compatibility with other versions of @code{make}.
+
+@item -C @var{dir}
+@cindex @code{-C}
+@itemx --directory=@var{dir}
+@cindex @code{--directory}
+Change to directory @var{dir} before reading the makefiles.  If multiple
+@samp{-C} options are specified, each is interpreted relative to the
+previous one: @samp{-C / -C etc} is equivalent to @samp{-C /etc}.
+This is typically used with recursive invocations of @code{make}
+(@pxref{Recursion, ,Recursive Use of @code{make}}).
+
+@item -d
+@cindex @code{-d}
+@c Extra blank line here makes the table look better.
+
+Print debugging information in addition to normal processing.  The
+debugging information says which files are being considered for
+remaking, which file-times are being compared and with what results,
+which files actually need to be remade, which implicit rules are
+considered and which are applied---everything interesting about how
+@code{make} decides what to do.  The @code{-d} option is equivalent to
+@samp{--debug=a} (see below).
+
+@item --debug[=@var{options}]
+@cindex @code{--debug}
+@c Extra blank line here makes the table look better.
+
+Print debugging information in addition to normal processing.  Various
+levels and types of output can be chosen.  With no arguments, print the
+``basic'' level of debugging.  Possible arguments are below; only the
+first character is considered, and values must be comma- or
+space-separated.
+
+@table @code
+@item a (@i{all})
+All types of debugging output are enabled.  This is equivalent to using
+@samp{-d}.
+
+@item b (@i{basic})
+Basic debugging prints each target that was found to be out-of-date, and
+whether the build was successful or not.
+
+@item v (@i{verbose})
+A level above @samp{basic}; includes messages about which makefiles were
+parsed, prerequisites that did not need to be rebuilt, etc.  This option
+also enables @samp{basic} messages.
+
+@item i (@i{implicit})
+Prints messages describing the implicit rule searches for each target.
+This option also enables @samp{basic} messages.
+
+@item j (@i{jobs})
+Prints messages giving details on the invocation of specific subcommands.
+
+@item m (@i{makefile})
+By default, the above messages are not enabled while trying to remake
+the makefiles.  This option enables messages while rebuilding makefiles,
+too.  Note that the @samp{all} option does enable this option.  This
+option also enables @samp{basic} messages.
+@end table
+
+@item -e
+@cindex @code{-e}
+@itemx --environment-overrides
+@cindex @code{--environment-overrides}
+Give variables taken from the environment precedence
+over variables from makefiles.
+@xref{Environment, ,Variables from the Environment}.
+
+@item -f @var{file}
+@cindex @code{-f}
+@itemx --file=@var{file}
+@cindex @code{--file}
+@itemx --makefile=@var{file}
+@cindex @code{--makefile}
+Read the file named @var{file} as a makefile.
+@xref{Makefiles, ,Writing Makefiles}.
+
+@item -h
+@cindex @code{-h}
+@itemx --help
+@cindex @code{--help}
+@c Extra blank line here makes the table look better.
+
+Remind you of the options that @code{make} understands and then exit.
+
+@item -i
+@cindex @code{-i}
+@itemx --ignore-errors
+@cindex @code{--ignore-errors}
+Ignore all errors in commands executed to remake files.
+@xref{Errors, ,Errors in Commands}.
+
+@item -I @var{dir}
+@cindex @code{-I}
+@itemx --include-dir=@var{dir}
+@cindex @code{--include-dir}
+Specifies a directory @var{dir} to search for included makefiles.
+@xref{Include, ,Including Other Makefiles}.  If several @samp{-I}
+options are used to specify several directories, the directories are
+searched in the order specified.
+
+@item -j [@var{jobs}]
+@cindex @code{-j}
+@itemx --jobs[=@var{jobs}]
+@cindex @code{--jobs}
+Specifies the number of jobs (commands) to run simultaneously.  With no
+argument, @code{make} runs as many jobs simultaneously as possible.  If
+there is more than one @samp{-j} option, the last one is effective.
+@xref{Parallel, ,Parallel Execution},
+for more information on how commands are run.
+Note that this option is ignored on MS-DOS.
+
+@item -k
+@cindex @code{-k}
+@itemx --keep-going
+@cindex @code{--keep-going}
+Continue as much as possible after an error.  While the target that
+failed, and those that depend on it, cannot be remade, the other
+prerequisites of these targets can be processed all the same.
+@xref{Testing, ,Testing the Compilation of a Program}.
+
+@item -l [@var{load}]
+@cindex @code{-l}
+@itemx --load-average[=@var{load}]
+@cindex @code{--load-average}
+@itemx --max-load[=@var{load}]
+@cindex @code{--max-load}
+Specifies that no new jobs (commands) should be started if there are
+other jobs running and the load average is at least @var{load} (a
+floating-point number).  With no argument, removes a previous load
+limit.  @xref{Parallel, ,Parallel Execution}.
+
+@item -n
+@cindex @code{-n}
+@itemx --just-print
+@cindex @code{--just-print}
+@itemx --dry-run
+@cindex @code{--dry-run}
+@itemx --recon
+@cindex @code{--recon}
+@c Extra blank line here makes the table look better.
+
+Print the commands that would be executed, but do not execute them.
+@xref{Instead of Execution, ,Instead of Executing the Commands}.
+
+@item -o @var{file}
+@cindex @code{-o}
+@itemx --old-file=@var{file}
+@cindex @code{--old-file}
+@itemx --assume-old=@var{file}
+@cindex @code{--assume-old}
+Do not remake the file @var{file} even if it is older than its
+prerequisites, and do not remake anything on account of changes in
+@var{file}.  Essentially the file is treated as very old and its rules
+are ignored.  @xref{Avoiding Compilation, ,Avoiding Recompilation of
+Some Files}.@refill
+
+@item -p
+@cindex @code{-p}
+@itemx --print-data-base
+@cindex @code{--print-data-base}
+@cindex data base of @code{make} rules
+@cindex predefined rules and variables, printing
+Print the data base (rules and variable values) that results from
+reading the makefiles; then execute as usual or as otherwise specified.
+This also prints the version information given by the @samp{-v} switch
+(see below).  To print the data base without trying to remake any files,
+use @w{@samp{make -qp}}.  To print the data base of predefined rules and
+variables, use @w{@samp{make -p -f /dev/null}}.  The data base output
+contains filename and linenumber information for command and variable
+definitions, so it can be a useful debugging tool in complex environments.
+
+@item -q
+@cindex @code{-q}
+@itemx --question
+@cindex @code{--question}
+``Question mode''.  Do not run any commands, or print anything; just
+return an exit status that is zero if the specified targets are already
+up to date, one if any remaking is required, or two if an error is
+encountered.  @xref{Instead of Execution, ,Instead of Executing the
+Commands}.@refill
+
+@item -r
+@cindex @code{-r}
+@itemx --no-builtin-rules
+@cindex @code{--no-builtin-rules}
+Eliminate use of the built-in implicit rules (@pxref{Implicit Rules,
+,Using Implicit Rules}).  You can still define your own by writing
+pattern rules (@pxref{Pattern Rules, ,Defining and Redefining Pattern
+Rules}).  The @samp{-r} option also clears out the default list of
+suffixes for suffix rules (@pxref{Suffix Rules, ,Old-Fashioned Suffix
+Rules}).  But you can still define your own suffixes with a rule for
+@code{.SUFFIXES}, and then define your own suffix rules.  Note that only
+@emph{rules} are affected by the @code{-r} option; default variables
+remain in effect (@pxref{Implicit Variables, ,Variables Used by Implicit
+Rules}); see the @samp{-R} option below.
+
+@item -R
+@cindex @code{-R}
+@itemx --no-builtin-variables
+@cindex @code{--no-builtin-variables}
+Eliminate use of the built-in rule-specific variables (@pxref{Implicit
+Variables, ,Variables Used by Implicit Rules}).  You can still define
+your own, of course.  The @samp{-R} option also automatically enables
+the @samp{-r} option (see above), since it doesn't make sense to have
+implicit rules without any definitions for the variables that they use.
+
+@item -s
+@cindex @code{-s}
+@itemx --silent
+@cindex @code{--silent}
+@itemx --quiet
+@cindex @code{--quiet}
+@c Extra blank line here makes the table look better.
+
+Silent operation; do not print the commands as they are executed.
+@xref{Echoing, ,Command Echoing}.
+
+@item -S
+@cindex @code{-S}
+@itemx --no-keep-going
+@cindex @code{--no-keep-going}
+@itemx --stop
+@cindex @code{--stop}
+@c Extra blank line here makes the table look better.
+
+Cancel the effect of the @samp{-k} option.  This is never necessary
+except in a recursive @code{make} where @samp{-k} might be inherited
+from the top-level @code{make} via @code{MAKEFLAGS}
+(@pxref{Recursion, ,Recursive Use of @code{make}})
+or if you set @samp{-k} in @code{MAKEFLAGS} in your environment.@refill
+
+@item -t
+@cindex @code{-t}
+@itemx --touch
+@cindex @code{--touch}
+@c Extra blank line here makes the table look better.
+
+Touch files (mark them up to date without really changing them)
+instead of running their commands.  This is used to pretend that the
+commands were done, in order to fool future invocations of
+@code{make}.  @xref{Instead of Execution, ,Instead of Executing the Commands}.
+
+@item -v
+@cindex @code{-v}
+@itemx --version
+@cindex @code{--version}
+Print the version of the @code{make} program plus a copyright, a list
+of authors, and a notice that there is no warranty; then exit.
+
+@item -w
+@cindex @code{-w}
+@itemx --print-directory
+@cindex @code{--print-directory}
+Print a message containing the working directory both before and after
+executing the makefile.  This may be useful for tracking down errors
+from complicated nests of recursive @code{make} commands.
+@xref{Recursion, ,Recursive Use of @code{make}}.  (In practice, you
+rarely need to specify this option since @samp{make} does it for you;
+see @ref{-w Option, ,The @samp{--print-directory} Option}.)
+
+@itemx --no-print-directory
+@cindex @code{--no-print-directory}
+Disable printing of the working directory under @code{-w}.
+This option is useful when @code{-w} is turned on automatically,
+but you do not want to see the extra messages.
+@xref{-w Option, ,The @samp{--print-directory} Option}.
+
+@item -W @var{file}
+@cindex @code{-W}
+@itemx --what-if=@var{file}
+@cindex @code{--what-if}
+@itemx --new-file=@var{file}
+@cindex @code{--new-file}
+@itemx --assume-new=@var{file}
+@cindex @code{--assume-new}
+Pretend that the target @var{file} has just been modified.  When used
+with the @samp{-n} flag, this shows you what would happen if you were
+to modify that file.  Without @samp{-n}, it is almost the same as
+running a @code{touch} command on the given file before running
+@code{make}, except that the modification time is changed only in the
+imagination of @code{make}.
+@xref{Instead of Execution, ,Instead of Executing the Commands}.
+
+@item --warn-undefined-variables
+@cindex @code{--warn-undefined-variables}
+@cindex variables, warning for undefined
+@cindex undefined variables, warning message
+Issue a warning message whenever @code{make} sees a reference to an
+undefined variable.  This can be helpful when you are trying to debug
+makefiles which use variables in complex ways.
+@end table
+
+@node Implicit Rules, Archives, Running, Top
+@chapter Using Implicit Rules
+@cindex implicit rule
+@cindex rule, implicit
+
+Certain standard ways of remaking target files are used very often.  For
+example, one customary way to make an object file is from a C source file
+using the C compiler, @code{cc}.
+
+@dfn{Implicit rules} tell @code{make} how to use customary techniques so
+that you do not have to specify them in detail when you want to use
+them.  For example, there is an implicit rule for C compilation.  File
+names determine which implicit rules are run.  For example, C
+compilation typically takes a @file{.c} file and makes a @file{.o} file.
+So @code{make} applies the implicit rule for C compilation when it sees
+this combination of file name endings.@refill
+
+A chain of implicit rules can apply in sequence; for example, @code{make}
+will remake a @file{.o} file from a @file{.y} file by way of a @file{.c} file.
+@iftex
+@xref{Chained Rules, ,Chains of Implicit Rules}.
+@end iftex
+
+The built-in implicit rules use several variables in their commands so
+that, by changing the values of the variables, you can change the way the
+implicit rule works.  For example, the variable @code{CFLAGS} controls the
+flags given to the C compiler by the implicit rule for C compilation.
+@iftex
+@xref{Implicit Variables, ,Variables Used by Implicit Rules}.
+@end iftex
+
+You can define your own implicit rules by writing @dfn{pattern rules}.
+@iftex
+@xref{Pattern Rules, ,Defining and Redefining Pattern Rules}.
+@end iftex
+
+@dfn{Suffix rules} are a more limited way to define implicit rules.
+Pattern rules are more general and clearer, but suffix rules are
+retained for compatibility.
+@iftex
+@xref{Suffix Rules, ,Old-Fashioned Suffix Rules}.
+@end iftex
+
+@menu
+* Using Implicit::              How to use an existing implicit rule
+                                  to get the commands for updating a file.
+* Catalogue of Rules::          A list of built-in implicit rules.
+* Implicit Variables::          How to change what predefined rules do.
+* Chained Rules::               How to use a chain of implicit rules.
+* Pattern Rules::               How to define new implicit rules.
+* Last Resort::                 How to defining commands for rules
+                                  which cannot find any.
+* Suffix Rules::                The old-fashioned style of implicit rule.
+* Implicit Rule Search::        The precise algorithm for applying
+                                  implicit rules.
+@end menu
+
+@node Using Implicit, Catalogue of Rules, Implicit Rules, Implicit Rules
+@section Using Implicit Rules
+@cindex implicit rule, how to use
+@cindex rule, implicit, how to use
+
+To allow @code{make} to find a customary method for updating a target file,
+all you have to do is refrain from specifying commands yourself.  Either
+write a rule with no command lines, or don't write a rule at all.  Then
+@code{make} will figure out which implicit rule to use based on which
+kind of source file exists or can be made.
+
+For example, suppose the makefile looks like this:
+
+@example
+foo : foo.o bar.o
+        cc -o foo foo.o bar.o $(CFLAGS) $(LDFLAGS)
+@end example
+
+@noindent
+Because you mention @file{foo.o} but do not give a rule for it, @code{make}
+will automatically look for an implicit rule that tells how to update it.
+This happens whether or not the file @file{foo.o} currently exists.
+
+If an implicit rule is found, it can supply both commands and one or
+more prerequisites (the source files).  You would want to write a rule
+for @file{foo.o} with no command lines if you need to specify additional
+prerequisites, such as header files, that the implicit rule cannot
+supply.
+
+Each implicit rule has a target pattern and prerequisite patterns.  There may
+be many implicit rules with the same target pattern.  For example, numerous
+rules make @samp{.o} files: one, from a @samp{.c} file with the C compiler;
+another, from a @samp{.p} file with the Pascal compiler; and so on.  The rule
+that actually applies is the one whose prerequisites exist or can be made.
+So, if you have a file @file{foo.c}, @code{make} will run the C compiler;
+otherwise, if you have a file @file{foo.p}, @code{make} will run the Pascal
+compiler; and so on.
+
+Of course, when you write the makefile, you know which implicit rule you
+want @code{make} to use, and you know it will choose that one because you
+know which possible prerequisite files are supposed to exist.
+@xref{Catalogue of Rules, ,Catalogue of Implicit Rules},
+for a catalogue of all the predefined implicit rules.
+
+Above, we said an implicit rule applies if the required prerequisites ``exist
+or can be made''.  A file ``can be made'' if it is mentioned explicitly in
+the makefile as a target or a prerequisite, or if an implicit rule can be
+recursively found for how to make it.  When an implicit prerequisite is the
+result of another implicit rule, we say that @dfn{chaining} is occurring.
+@xref{Chained Rules, ,Chains of Implicit Rules}.
+
+In general, @code{make} searches for an implicit rule for each target, and
+for each double-colon rule, that has no commands.  A file that is mentioned
+only as a prerequisite is considered a target whose rule specifies nothing,
+so implicit rule search happens for it.  @xref{Implicit Rule Search, ,Implicit Rule Search Algorithm}, for the
+details of how the search is done.
+
+Note that explicit prerequisites do not influence implicit rule search.
+For example, consider this explicit rule:
+
+@example
+foo.o: foo.p
+@end example
+
+@noindent
+The prerequisite on @file{foo.p} does not necessarily mean that
+@code{make} will remake @file{foo.o} according to the implicit rule to
+make an object file, a @file{.o} file, from a Pascal source file, a
+@file{.p} file.  For example, if @file{foo.c} also exists, the implicit
+rule to make an object file from a C source file is used instead,
+because it appears before the Pascal rule in the list of predefined
+implicit rules (@pxref{Catalogue of Rules, , Catalogue of Implicit
+Rules}).
+
+If you do not want an implicit rule to be used for a target that has no
+commands, you can give that target empty commands by writing a semicolon
+(@pxref{Empty Commands, ,Defining Empty Commands}).
+
+@node Catalogue of Rules, Implicit Variables, Using Implicit, Implicit Rules
+@section Catalogue of Implicit Rules
+@cindex implicit rule, predefined
+@cindex rule, implicit, predefined
+
+Here is a catalogue of predefined implicit rules which are always
+available unless the makefile explicitly overrides or cancels them.
+@xref{Canceling Rules, ,Canceling Implicit Rules}, for information on
+canceling or overriding an implicit rule.  The @samp{-r} or
+@samp{--no-builtin-rules} option cancels all predefined rules.
+
+Not all of these rules will always be defined, even when the @samp{-r}
+option is not given.  Many of the predefined implicit rules are
+implemented in @code{make} as suffix rules, so which ones will be
+defined depends on the @dfn{suffix list} (the list of prerequisites of
+the special target @code{.SUFFIXES}).  The default suffix list is:
+@code{.out}, @code{.a}, @code{.ln}, @code{.o}, @code{.c}, @code{.cc},
+@code{.C}, @code{.p}, @code{.f}, @code{.F}, @code{.r}, @code{.y},
+@code{.l}, @code{.s}, @code{.S}, @code{.mod}, @code{.sym}, @code{.def},
+@code{.h}, @code{.info}, @code{.dvi}, @code{.tex}, @code{.texinfo},
+@code{.texi}, @code{.txinfo}, @code{.w}, @code{.ch} @code{.web},
+@code{.sh}, @code{.elc}, @code{.el}.  All of the implicit rules
+described below whose prerequisites have one of these suffixes are
+actually suffix rules.  If you modify the suffix list, the only
+predefined suffix rules in effect will be those named by one or two of
+the suffixes that are on the list you specify; rules whose suffixes fail
+to be on the list are disabled.  @xref{Suffix Rules, ,Old-Fashioned
+Suffix Rules}, for full details on suffix rules.
+
+@table @asis
+@item Compiling C programs
+@cindex C, rule to compile
+@pindex cc
+@pindex gcc
+@pindex .o
+@pindex .c
+@file{@var{n}.o} is made automatically from @file{@var{n}.c} with
+a command of the form @samp{$(CC) -c $(CPPFLAGS) $(CFLAGS)}.@refill
+
+@item Compiling C++ programs
+@cindex C++, rule to compile
+@pindex g++
+@pindex .C
+@pindex .cc
+@file{@var{n}.o} is made automatically from @file{@var{n}.cc} or
+@file{@var{n}.C} with a command of the form @samp{$(CXX) -c $(CPPFLAGS)
+$(CXXFLAGS)}.  We encourage you to use the suffix @samp{.cc} for C++
+source files instead of @samp{.C}.@refill
+
+@item Compiling Pascal programs
+@cindex Pascal, rule to compile
+@pindex pc
+@pindex .p
+@file{@var{n}.o} is made automatically from @file{@var{n}.p}
+with the command @samp{$(PC) -c $(PFLAGS)}.@refill
+
+@item Compiling Fortran and Ratfor programs
+@cindex Fortran, rule to compile
+@cindex Ratfor, rule to compile
+@pindex f77
+@pindex .f
+@pindex .r
+@pindex .F
+@file{@var{n}.o} is made automatically from @file{@var{n}.r},
+@file{@var{n}.F} or @file{@var{n}.f} by running the
+Fortran compiler.  The precise command used is as follows:@refill
+
+@table @samp
+@item .f
+@samp{$(FC) -c $(FFLAGS)}.
+@item .F
+@samp{$(FC) -c $(FFLAGS) $(CPPFLAGS)}.
+@item .r
+@samp{$(FC) -c $(FFLAGS) $(RFLAGS)}.
+@end table
+
+@item Preprocessing Fortran and Ratfor programs
+@file{@var{n}.f} is made automatically from @file{@var{n}.r} or
+@file{@var{n}.F}.  This rule runs just the preprocessor to convert a
+Ratfor or preprocessable Fortran program into a strict Fortran
+program.  The precise command used is as follows:@refill
+
+@table @samp
+@item .F
+@samp{$(FC) -F $(CPPFLAGS) $(FFLAGS)}.
+@item .r
+@samp{$(FC) -F $(FFLAGS) $(RFLAGS)}.
+@end table
+
+@item Compiling Modula-2 programs
+@cindex Modula-2, rule to compile
+@pindex m2c
+@pindex .sym
+@pindex .def
+@pindex .mod
+@file{@var{n}.sym} is made from @file{@var{n}.def} with a command
+of the form @samp{$(M2C) $(M2FLAGS) $(DEFFLAGS)}.  @file{@var{n}.o}
+is made from @file{@var{n}.mod}; the form is:
+@w{@samp{$(M2C) $(M2FLAGS) $(MODFLAGS)}}.@refill
+
+@need 1200
+@item Assembling and preprocessing assembler programs
+@cindex assembly, rule to compile
+@pindex as
+@pindex .s
+@file{@var{n}.o} is made automatically from @file{@var{n}.s} by
+running the assembler, @code{as}.  The precise command is
+@samp{$(AS) $(ASFLAGS)}.@refill
+
+@pindex .S
+@file{@var{n}.s} is made automatically from @file{@var{n}.S} by
+running the C preprocessor, @code{cpp}.  The precise command is
+@w{@samp{$(CPP) $(CPPFLAGS)}}.
+
+@item Linking a single object file
+@cindex linking, predefined rule for
+@pindex ld
+@pindex .o
+@file{@var{n}} is made automatically from @file{@var{n}.o} by running
+the linker (usually called @code{ld}) via the C compiler.  The precise
+command used is @w{@samp{$(CC) $(LDFLAGS) @var{n}.o $(LOADLIBES) $(LDLIBS)}}.
+
+This rule does the right thing for a simple program with only one
+source file.  It will also do the right thing if there are multiple
+object files (presumably coming from various other source files), one
+of which has a name matching that of the executable file.  Thus,
+
+@example
+x: y.o z.o
+@end example
+
+@noindent
+when @file{x.c}, @file{y.c} and @file{z.c} all exist will execute:
+
+@example
+@group
+cc -c x.c -o x.o
+cc -c y.c -o y.o
+cc -c z.c -o z.o
+cc x.o y.o z.o -o x
+rm -f x.o
+rm -f y.o
+rm -f z.o
+@end group
+@end example
+
+@noindent
+In more complicated cases, such as when there is no object file whose
+name derives from the executable file name, you must write an explicit
+command for linking.
+
+Each kind of file automatically made into @samp{.o} object files will
+be automatically linked by using the compiler (@samp{$(CC)},
+@samp{$(FC)} or @samp{$(PC)}; the C compiler @samp{$(CC)} is used to
+assemble @samp{.s} files) without the @samp{-c} option.  This could be
+done by using the @samp{.o} object files as intermediates, but it is
+faster to do the compiling and linking in one step, so that's how it's
+done.@refill
+
+@item Yacc for C programs
+@pindex yacc
+@cindex Yacc, rule to run
+@pindex .y
+@file{@var{n}.c} is made automatically from @file{@var{n}.y} by
+running Yacc with the command @samp{$(YACC) $(YFLAGS)}.
+
+@item Lex for C programs
+@pindex lex
+@cindex Lex, rule to run
+@pindex .l
+@file{@var{n}.c} is made automatically from @file{@var{n}.l} by
+running Lex.  The actual command is @samp{$(LEX) $(LFLAGS)}.
+
+@item Lex for Ratfor programs
+@file{@var{n}.r} is made automatically from @file{@var{n}.l} by
+running Lex.  The actual command is @samp{$(LEX) $(LFLAGS)}.
+
+The convention of using the same suffix @samp{.l} for all Lex files
+regardless of whether they produce C code or Ratfor code makes it
+impossible for @code{make} to determine automatically which of the two
+languages you are using in any particular case.  If @code{make} is
+called upon to remake an object file from a @samp{.l} file, it must
+guess which compiler to use.  It will guess the C compiler, because
+that is more common.  If you are using Ratfor, make sure @code{make}
+knows this by mentioning @file{@var{n}.r} in the makefile.  Or, if you
+are using Ratfor exclusively, with no C files, remove @samp{.c} from
+the list of implicit rule suffixes with:@refill
+
+@example
+@group
+.SUFFIXES:
+.SUFFIXES: .o .r .f .l @dots{}
+@end group
+@end example
+
+@item Making Lint Libraries from C, Yacc, or Lex programs
+@pindex lint
+@cindex @code{lint}, rule to run
+@pindex .ln
+@file{@var{n}.ln} is made from @file{@var{n}.c} by running @code{lint}.
+The precise command is @w{@samp{$(LINT) $(LINTFLAGS) $(CPPFLAGS) -i}}.
+The same command is used on the C code produced from
+@file{@var{n}.y} or @file{@var{n}.l}.@refill
+
+@item @TeX{} and Web
+@cindex @TeX{}, rule to run
+@cindex Web, rule to run
+@pindex tex
+@pindex cweave
+@pindex weave
+@pindex tangle
+@pindex ctangle
+@pindex .dvi
+@pindex .tex
+@pindex .web
+@pindex .w
+@pindex .ch
+@file{@var{n}.dvi} is made from @file{@var{n}.tex} with the command
+@samp{$(TEX)}.  @file{@var{n}.tex} is made from @file{@var{n}.web} with
+@samp{$(WEAVE)}, or from @file{@var{n}.w} (and from @file{@var{n}.ch} if
+it exists or can be made) with @samp{$(CWEAVE)}.  @file{@var{n}.p} is
+made from @file{@var{n}.web} with @samp{$(TANGLE)} and @file{@var{n}.c}
+is made from @file{@var{n}.w} (and from @file{@var{n}.ch} if it exists
+or can be made) with @samp{$(CTANGLE)}.@refill
+
+@item Texinfo and Info
+@cindex Texinfo, rule to format
+@cindex Info, rule to format
+@pindex texi2dvi
+@pindex makeinfo
+@pindex .texinfo
+@pindex .info
+@pindex .texi
+@pindex .txinfo
+@file{@var{n}.dvi} is made from @file{@var{n}.texinfo},
+@file{@var{n}.texi}, or @file{@var{n}.txinfo}, with the command
+@w{@samp{$(TEXI2DVI) $(TEXI2DVI_FLAGS)}}.  @file{@var{n}.info} is made from
+@file{@var{n}.texinfo}, @file{@var{n}.texi}, or @file{@var{n}.txinfo}, with
+the command @w{@samp{$(MAKEINFO) $(MAKEINFO_FLAGS)}}.
+
+@item RCS
+@cindex RCS, rule to extract from
+@pindex co
+@pindex ,v @r{(RCS file extension)}
+Any file @file{@var{n}} is extracted if necessary from an RCS file
+named either @file{@var{n},v} or @file{RCS/@var{n},v}.  The precise
+command used is @w{@samp{$(CO) $(COFLAGS)}}.  @file{@var{n}} will not be
+extracted from RCS if it already exists, even if the RCS file is
+newer.  The rules for RCS are terminal
+(@pxref{Match-Anything Rules, ,Match-Anything Pattern Rules}),
+so RCS files cannot be generated from another source; they must
+actually exist.@refill
+
+@item SCCS
+@cindex SCCS, rule to extract from
+@pindex get
+@pindex s. @r{(SCCS file prefix)}
+Any file @file{@var{n}} is extracted if necessary from an SCCS file
+named either @file{s.@var{n}} or @file{SCCS/s.@var{n}}.  The precise
+command used is @w{@samp{$(GET) $(GFLAGS)}}.  The rules for SCCS are
+terminal (@pxref{Match-Anything Rules, ,Match-Anything Pattern Rules}),
+so SCCS files cannot be generated from another source; they must
+actually exist.@refill
+
+@pindex .sh
+For the benefit of SCCS, a file @file{@var{n}} is copied from
+@file{@var{n}.sh} and made executable (by everyone).  This is for
+shell scripts that are checked into SCCS.  Since RCS preserves the
+execution permission of a file, you do not need to use this feature
+with RCS.@refill
+
+We recommend that you avoid using of SCCS.  RCS is widely held to be
+superior, and is also free.  By choosing free software in place of
+comparable (or inferior) proprietary software, you support the free
+software movement.
+@end table
+
+Usually, you want to change only the variables listed in the table
+above, which are documented in the following section.
+
+However, the commands in built-in implicit rules actually use
+variables such as @code{COMPILE.c}, @code{LINK.p}, and
+@code{PREPROCESS.S}, whose values contain the commands listed above.
+
+@code{make} follows the convention that the rule to compile a
+@file{.@var{x}} source file uses the variable @code{COMPILE.@var{x}}.
+Similarly, the rule to produce an executable from a @file{.@var{x}}
+file uses @code{LINK.@var{x}}; and the rule to preprocess a
+@file{.@var{x}} file uses @code{PREPROCESS.@var{x}}.
+
+@vindex OUTPUT_OPTION
+Every rule that produces an object file uses the variable
+@code{OUTPUT_OPTION}.  @code{make} defines this variable either to
+contain @samp{-o $@@}, or to be empty, depending on a compile-time
+option.  You need the @samp{-o} option to ensure that the output goes
+into the right file when the source file is in a different directory,
+as when using @code{VPATH} (@pxref{Directory Search}).  However,
+compilers on some systems do not accept a @samp{-o} switch for object
+files.  If you use such a system, and use @code{VPATH}, some
+compilations will put their output in the wrong place.
+A possible workaround for this problem is to give @code{OUTPUT_OPTION}
+the value @w{@samp{; mv $*.o $@@}}.
+
+@node Implicit Variables, Chained Rules, Catalogue of Rules, Implicit Rules
+@section Variables Used by Implicit Rules
+@cindex flags for compilers
+
+The commands in built-in implicit rules make liberal use of certain
+predefined variables.  You can alter these variables in the makefile,
+with arguments to @code{make}, or in the environment to alter how the
+implicit rules work without redefining the rules themselves.  You can
+cancel all variables used by implicit rules with the @samp{-R} or
+@samp{--no-builtin-variables} option.
+
+For example, the command used to compile a C source file actually says
+@samp{$(CC) -c $(CFLAGS) $(CPPFLAGS)}.  The default values of the variables
+used are @samp{cc} and nothing, resulting in the command @samp{cc -c}.  By
+redefining @samp{CC} to @samp{ncc}, you could cause @samp{ncc} to be
+used for all C compilations performed by the implicit rule.  By redefining
+@samp{CFLAGS} to be @samp{-g}, you could pass the @samp{-g} option to
+each compilation.  @emph{All} implicit rules that do C compilation use
+@samp{$(CC)} to get the program name for the compiler and @emph{all}
+include @samp{$(CFLAGS)} among the arguments given to the compiler.@refill
+
+The variables used in implicit rules fall into two classes: those that are
+names of programs (like @code{CC}) and those that contain arguments for the
+programs (like @code{CFLAGS}).  (The ``name of a program'' may also contain
+some command arguments, but it must start with an actual executable program
+name.)  If a variable value contains more than one argument, separate them
+with spaces.
+
+Here is a table of variables used as names of programs in built-in rules:
+
+@table @code
+@item AR
+@vindex AR
+Archive-maintaining program; default @samp{ar}.
+@pindex ar
+
+@item AS
+@vindex AS
+Program for doing assembly; default @samp{as}.
+@pindex as
+
+@item CC
+@vindex CC
+Program for compiling C programs; default @samp{cc}.
+@pindex cc
+
+@item CXX
+@vindex CXX
+Program for compiling C++ programs; default @samp{g++}.
+@pindex g++
+
+@item CO
+@vindex CO
+Program for extracting a file from RCS; default @samp{co}.
+@pindex co
+
+@item CPP
+@vindex CPP
+Program for running the C preprocessor, with results to standard output;
+default @samp{$(CC) -E}.
+
+@item FC
+@vindex FC
+Program for compiling or preprocessing Fortran and Ratfor programs;
+default @samp{f77}.
+@pindex f77
+
+@item GET
+@vindex GET
+Program for extracting a file from SCCS; default @samp{get}.
+@pindex get
+
+@item LEX
+@vindex LEX
+Program to use to turn Lex grammars into C programs or Ratfor programs;
+default @samp{lex}.
+@pindex lex
+
+@item PC
+@vindex PC
+Program for compiling Pascal programs; default @samp{pc}.
+@pindex pc
+
+@item YACC
+@vindex YACC
+Program to use to turn Yacc grammars into C programs; default @samp{yacc}.
+@pindex yacc
+
+@item YACCR
+@vindex YACCR
+Program to use to turn Yacc grammars into Ratfor
+programs; default @samp{yacc -r}.
+
+@item MAKEINFO
+@vindex MAKEINFO
+Program to convert a Texinfo source file into an Info file; default
+@samp{makeinfo}.
+@pindex makeinfo
+
+@item TEX
+@vindex TEX
+Program to make @TeX{} @sc{dvi} files from @TeX{} source;
+default @samp{tex}.
+@pindex tex
+
+@item TEXI2DVI
+@vindex TEXI2DVI
+Program to make @TeX{} @sc{dvi} files from Texinfo source;
+default @samp{texi2dvi}.
+@pindex texi2dvi
+
+@item WEAVE
+@vindex WEAVE
+Program to translate Web into @TeX{}; default @samp{weave}.
+@pindex weave
+
+@item CWEAVE
+@vindex CWEAVE
+Program to translate C Web into @TeX{}; default @samp{cweave}.
+@pindex cweave
+
+@item TANGLE
+@vindex TANGLE
+Program to translate Web into Pascal; default @samp{tangle}.
+@pindex tangle
+
+@item CTANGLE
+@vindex CTANGLE
+Program to translate C Web into C; default @samp{ctangle}.
+@pindex ctangle
+
+@item RM
+@vindex RM
+Command to remove a file; default @samp{rm -f}.
+@pindex rm
+@end table
+
+Here is a table of variables whose values are additional arguments for the
+programs above.  The default values for all of these is the empty
+string, unless otherwise noted.
+
+@table @code
+@item ARFLAGS
+@vindex ARFLAGS
+Flags to give the archive-maintaining program; default @samp{rv}.
+
+@item ASFLAGS
+@vindex ASFLAGS
+Extra flags to give to the assembler (when explicitly
+invoked on a @samp{.s} or @samp{.S} file).
+
+@item CFLAGS
+@vindex CFLAGS
+Extra flags to give to the C compiler.
+
+@item CXXFLAGS
+@vindex CXXFLAGS
+Extra flags to give to the C++ compiler.
+
+@item COFLAGS
+@vindex COFLAGS
+Extra flags to give to the RCS @code{co} program.
+
+@item CPPFLAGS
+@vindex CPPFLAGS
+Extra flags to give to the C preprocessor and programs
+that use it (the C and Fortran compilers).
+
+@item FFLAGS
+@vindex FFLAGS
+Extra flags to give to the Fortran compiler.
+
+@item GFLAGS
+@vindex GFLAGS
+Extra flags to give to the SCCS @code{get} program.
+
+@item LDFLAGS
+@vindex LDFLAGS
+Extra flags to give to compilers when they are
+supposed to invoke the linker, @samp{ld}.
+
+@item LFLAGS
+@vindex LFLAGS
+Extra flags to give to Lex.
+
+@item PFLAGS
+@vindex PFLAGS
+Extra flags to give to the Pascal compiler.
+
+@item RFLAGS
+@vindex RFLAGS
+Extra flags to give to the Fortran compiler for Ratfor programs.
+
+@item YFLAGS
+@vindex YFLAGS
+Extra flags to give to Yacc.
+@end table
+
+@node Chained Rules, Pattern Rules, Implicit Variables, Implicit Rules
+@section Chains of Implicit Rules
+
+@cindex chains of rules
+@cindex rule, implicit, chains of
+Sometimes a file can be made by a sequence of implicit rules.  For example,
+a file @file{@var{n}.o} could be made from @file{@var{n}.y} by running
+first Yacc and then @code{cc}.  Such a sequence is called a @dfn{chain}.
+
+If the file @file{@var{n}.c} exists, or is mentioned in the makefile, no
+special searching is required: @code{make} finds that the object file can
+be made by C compilation from @file{@var{n}.c}; later on, when considering
+how to make @file{@var{n}.c}, the rule for running Yacc is
+used.  Ultimately both @file{@var{n}.c} and @file{@var{n}.o} are
+updated.@refill
+
+@cindex intermediate files
+@cindex files, intermediate
+However, even if @file{@var{n}.c} does not exist and is not mentioned,
+@code{make} knows how to envision it as the missing link between
+@file{@var{n}.o} and @file{@var{n}.y}!  In this case, @file{@var{n}.c} is
+called an @dfn{intermediate file}.  Once @code{make} has decided to use the
+intermediate file, it is entered in the data base as if it had been
+mentioned in the makefile, along with the implicit rule that says how to
+create it.@refill
+
+Intermediate files are remade using their rules just like all other
+files.  But intermediate files are treated differently in two ways.
+
+The first difference is what happens if the intermediate file does not
+exist.  If an ordinary file @var{b} does not exist, and @code{make}
+considers a target that depends on @var{b}, it invariably creates
+@var{b} and then updates the target from @var{b}.  But if @var{b} is an
+intermediate file, then @code{make} can leave well enough alone.  It
+won't bother updating @var{b}, or the ultimate target, unless some
+prerequisite of @var{b} is newer than that target or there is some other
+reason to update that target.
+
+The second difference is that if @code{make} @emph{does} create @var{b}
+in order to update something else, it deletes @var{b} later on after it
+is no longer needed.  Therefore, an intermediate file which did not
+exist before @code{make} also does not exist after @code{make}.
+@code{make} reports the deletion to you by printing a @samp{rm -f}
+command showing which file it is deleting.
+
+Ordinarily, a file cannot be intermediate if it is mentioned in the
+makefile as a target or prerequisite.  However, you can explicitly mark a
+file as intermediate by listing it as a prerequisite of the special target
+@code{.INTERMEDIATE}.  This takes effect even if the file is mentioned
+explicitly in some other way.
+
+@cindex intermediate files, preserving
+@cindex preserving intermediate files
+@cindex secondary files
+You can prevent automatic deletion of an intermediate file by marking it
+as a @dfn{secondary} file.  To do this, list it as a prerequisite of the
+special target @code{.SECONDARY}.  When a file is secondary, @code{make}
+will not create the file merely because it does not already exist, but
+@code{make} does not automatically delete the file.  Marking a file as
+secondary also marks it as intermediate.
+
+You can list the target pattern of an implicit rule (such as @samp{%.o})
+as a prerequisite of the special target @code{.PRECIOUS} to preserve
+intermediate files made by implicit rules whose target patterns match
+that file's name; see @ref{Interrupts}.@refill
+@cindex preserving with @code{.PRECIOUS}
+@cindex @code{.PRECIOUS} intermediate files
+
+A chain can involve more than two implicit rules.  For example, it is
+possible to make a file @file{foo} from @file{RCS/foo.y,v} by running RCS,
+Yacc and @code{cc}.  Then both @file{foo.y} and @file{foo.c} are
+intermediate files that are deleted at the end.@refill
+
+No single implicit rule can appear more than once in a chain.  This means
+that @code{make} will not even consider such a ridiculous thing as making
+@file{foo} from @file{foo.o.o} by running the linker twice.  This
+constraint has the added benefit of preventing any infinite loop in the
+search for an implicit rule chain.
+
+There are some special implicit rules to optimize certain cases that would
+otherwise be handled by rule chains.  For example, making @file{foo} from
+@file{foo.c} could be handled by compiling and linking with separate
+chained rules, using @file{foo.o} as an intermediate file.  But what
+actually happens is that a special rule for this case does the compilation
+and linking with a single @code{cc} command.  The optimized rule is used in
+preference to the step-by-step chain because it comes earlier in the
+ordering of rules.
+
+@node Pattern Rules, Last Resort, Chained Rules, Implicit Rules
+@section Defining and Redefining Pattern Rules
+
+You define an implicit rule by writing a @dfn{pattern rule}.  A pattern
+rule looks like an ordinary rule, except that its target contains the
+character @samp{%} (exactly one of them).  The target is considered a
+pattern for matching file names; the @samp{%} can match any nonempty
+substring, while other characters match only themselves.  The prerequisites
+likewise use @samp{%} to show how their names relate to the target name.
+
+Thus, a pattern rule @samp{%.o : %.c} says how to make any file
+@file{@var{stem}.o} from another file @file{@var{stem}.c}.@refill
+
+Note that expansion using @samp{%} in pattern rules occurs
+@strong{after} any variable or function expansions, which take place
+when the makefile is read.  @xref{Using Variables, , How to Use
+Variables}, and @ref{Functions, ,Functions for Transforming Text}.
+
+@menu
+* Pattern Intro::               An introduction to pattern rules.
+* Pattern Examples::            Examples of pattern rules.
+* Automatic::                   How to use automatic variables in the
+                                  commands of implicit rules.
+* Pattern Match::               How patterns match.
+* Match-Anything Rules::        Precautions you should take prior to
+                                  defining rules that can match any
+                                  target file whatever.
+* Canceling Rules::             How to override or cancel built-in rules.
+@end menu
+
+@node Pattern Intro, Pattern Examples, Pattern Rules, Pattern Rules
+@subsection Introduction to Pattern Rules
+@cindex pattern rule
+@cindex rule, pattern
+
+A pattern rule contains the character @samp{%} (exactly one of them)
+in the target; otherwise, it looks exactly like an ordinary rule.  The
+target is a pattern for matching file names; the @samp{%} matches any
+nonempty substring, while other characters match only themselves.
+@cindex target pattern, implicit
+@cindex @code{%}, in pattern rules
+
+For example, @samp{%.c} as a pattern matches any file name that ends in
+@samp{.c}.  @samp{s.%.c} as a pattern matches any file name that starts
+with @samp{s.}, ends in @samp{.c} and is at least five characters long.
+(There must be at least one character to match the @samp{%}.)  The substring
+that the @samp{%} matches is called the @dfn{stem}.@refill
+
+@samp{%} in a prerequisite of a pattern rule stands for the same stem
+that was matched by the @samp{%} in the target.  In order for
+the pattern rule to apply, its target pattern must match the file name
+under consideration, and its prerequisite patterns must name files that
+exist or can be made.  These files become prerequisites of the target.
+@cindex prerequisite pattern, implicit
+
+Thus, a rule of the form
+
+@example
+%.o : %.c ; @var{command}@dots{}
+@end example
+
+@noindent
+specifies how to make a file @file{@var{n}.o}, with another file
+@file{@var{n}.c} as its prerequisite, provided that @file{@var{n}.c}
+exists or can be made.
+
+There may also be prerequisites that do not use @samp{%}; such a prerequisite
+attaches to every file made by this pattern rule.  These unvarying
+prerequisites are useful occasionally.
+
+A pattern rule need not have any prerequisites that contain @samp{%}, or
+in fact any prerequisites at all.  Such a rule is effectively a general
+wildcard.  It provides a way to make any file that matches the target
+pattern.  @xref{Last Resort}.
+
+@c !!! The end of of this paragraph should be rewritten.  --bob
+Pattern rules may have more than one target.  Unlike normal rules, this
+does not act as many different rules with the same prerequisites and
+commands.  If a pattern rule has multiple targets, @code{make} knows that
+the rule's commands are responsible for making all of the targets.  The
+commands are executed only once to make all the targets.  When searching
+for a pattern rule to match a target, the target patterns of a rule other
+than the one that matches the target in need of a rule are incidental:
+@code{make} worries only about giving commands and prerequisites to the file
+presently in question.  However, when this file's commands are run, the
+other targets are marked as having been updated themselves.
+@cindex multiple targets, in pattern rule
+@cindex target, multiple in pattern rule
+
+The order in which pattern rules appear in the makefile is important
+since this is the order in which they are considered.
+Of equally applicable
+rules, only the first one found is used.  The rules you write take precedence
+over those that are built in.  Note however, that a rule whose
+prerequisites actually exist or are mentioned always takes priority over a
+rule with prerequisites that must be made by chaining other implicit rules.
+@cindex pattern rules, order of
+@cindex order of pattern rules
+
+@node Pattern Examples, Automatic, Pattern Intro, Pattern Rules
+@subsection Pattern Rule Examples
+
+Here are some examples of pattern rules actually predefined in
+@code{make}.  First, the rule that compiles @samp{.c} files into @samp{.o}
+files:@refill
+
+@example
+%.o : %.c
+        $(CC) -c $(CFLAGS) $(CPPFLAGS) $< -o $@@
+@end example
+
+@noindent
+defines a rule that can make any file @file{@var{x}.o} from
+@file{@var{x}.c}.  The command uses the automatic variables @samp{$@@} and
+@samp{$<} to substitute the names of the target file and the source file
+in each case where the rule applies (@pxref{Automatic, ,Automatic Variables}).@refill
+
+Here is a second built-in rule:
+
+@example
+% :: RCS/%,v
+        $(CO) $(COFLAGS) $<
+@end example
+
+@noindent
+defines a rule that can make any file @file{@var{x}} whatsoever from a
+corresponding file @file{@var{x},v} in the subdirectory @file{RCS}.  Since
+the target is @samp{%}, this rule will apply to any file whatever, provided
+the appropriate prerequisite file exists.  The double colon makes the rule
+@dfn{terminal}, which means that its prerequisite may not be an intermediate
+file (@pxref{Match-Anything Rules, ,Match-Anything Pattern Rules}).@refill
+
+@need 500
+This pattern rule has two targets:
+
+@example
+@group
+%.tab.c %.tab.h: %.y
+        bison -d $<
+@end group
+@end example
+
+@noindent
+@c The following paragraph is rewritten to avoid overfull hboxes
+This tells @code{make} that the command @samp{bison -d @var{x}.y} will
+make both @file{@var{x}.tab.c} and @file{@var{x}.tab.h}.  If the file
+@file{foo} depends on the files @file{parse.tab.o} and @file{scan.o}
+and the file @file{scan.o} depends on the file @file{parse.tab.h},
+when @file{parse.y} is changed, the command @samp{bison -d parse.y}
+will be executed only once, and the prerequisites of both
+@file{parse.tab.o} and @file{scan.o} will be satisfied.  (Presumably
+the file @file{parse.tab.o} will be recompiled from @file{parse.tab.c}
+and the file @file{scan.o} from @file{scan.c}, while @file{foo} is
+linked from @file{parse.tab.o}, @file{scan.o}, and its other
+prerequisites, and it will execute happily ever after.)@refill
+
+@node Automatic, Pattern Match, Pattern Examples, Pattern Rules
+@subsection Automatic Variables
+@cindex automatic variables
+@cindex variables, automatic
+@cindex variables, and implicit rule
+
+Suppose you are writing a pattern rule to compile a @samp{.c} file into a
+@samp{.o} file: how do you write the @samp{cc} command so that it operates
+on the right source file name?  You cannot write the name in the command,
+because the name is different each time the implicit rule is applied.
+
+What you do is use a special feature of @code{make}, the @dfn{automatic
+variables}.  These variables have values computed afresh for each rule that
+is executed, based on the target and prerequisites of the rule.  In this
+example, you would use @samp{$@@} for the object file name and @samp{$<}
+for the source file name.
+
+Here is a table of automatic variables:
+
+@table @code
+@vindex $@@
+@vindex @@ @r{(automatic variable)}
+@item $@@
+The file name of the target of the rule.  If the target is an archive
+member, then @samp{$@@} is the name of the archive file.  In a pattern
+rule that has multiple targets (@pxref{Pattern Intro, ,Introduction to
+Pattern Rules}), @samp{$@@} is the name of whichever target caused the
+rule's commands to be run.
+
+@vindex $%
+@vindex % @r{(automatic variable)}
+@item $%
+The target member name, when the target is an archive member.
+@xref{Archives}.  For example, if the target is @file{foo.a(bar.o)} then
+@samp{$%} is @file{bar.o} and @samp{$@@} is @file{foo.a}.  @samp{$%} is
+empty when the target is not an archive member.
+
+@vindex $<
+@vindex < @r{(automatic variable)}
+@item $<
+The name of the first prerequisite.  If the target got its commands from
+an implicit rule, this will be the first prerequisite added by the
+implicit rule (@pxref{Implicit Rules}).
+
+@vindex $?
+@vindex ? @r{(automatic variable)}
+@item $?
+The names of all the prerequisites that are newer than the target, with
+spaces between them.  For prerequisites which are archive members, only
+the member named is used (@pxref{Archives}).
+@cindex prerequisites, list of changed
+@cindex list of changed prerequisites
+
+@vindex $^
+@vindex ^ @r{(automatic variable)}
+@item $^
+The names of all the prerequisites, with spaces between them.  For
+prerequisites which are archive members, only the member named is used
+(@pxref{Archives}).  A target has only one prerequisite on each other file
+it depends on, no matter how many times each file is listed as a
+prerequisite.  So if you list a prerequisite more than once for a target,
+the value of @code{$^} contains just one copy of the name.
+@cindex prerequisites, list of all
+@cindex list of all prerequisites
+
+@vindex $+
+@vindex + @r{(automatic variable)}
+@item $+
+This is like @samp{$^}, but prerequisites listed more than once are
+duplicated in the order they were listed in the makefile.  This is
+primarily useful for use in linking commands where it is meaningful to
+repeat library file names in a particular order.
+
+@vindex $*
+@vindex * @r{(automatic variable)}
+@item $*
+The stem with which an implicit rule matches (@pxref{Pattern Match, ,How
+Patterns Match}).  If the target is @file{dir/a.foo.b} and the target
+pattern is @file{a.%.b} then the stem is @file{dir/foo}.  The stem is
+useful for constructing names of related files.@refill
+@cindex stem, variable for
+
+In a static pattern rule, the stem is part of the file name that matched
+the @samp{%} in the target pattern.
+
+In an explicit rule, there is no stem; so @samp{$*} cannot be determined
+in that way.  Instead, if the target name ends with a recognized suffix
+(@pxref{Suffix Rules, ,Old-Fashioned Suffix Rules}), @samp{$*} is set to
+the target name minus the suffix.  For example, if the target name is
+@samp{foo.c}, then @samp{$*} is set to @samp{foo}, since @samp{.c} is a
+suffix.  GNU @code{make} does this bizarre thing only for compatibility
+with other implementations of @code{make}.  You should generally avoid
+using @samp{$*} except in implicit rules or static pattern rules.@refill
+
+If the target name in an explicit rule does not end with a recognized
+suffix, @samp{$*} is set to the empty string for that rule.
+@end table
+
+@samp{$?} is useful even in explicit rules when you wish to operate on only
+the prerequisites that have changed.  For example, suppose that an archive
+named @file{lib} is supposed to contain copies of several object files.
+This rule copies just the changed object files into the archive:
+
+@example
+@group
+lib: foo.o bar.o lose.o win.o
+        ar r lib $?
+@end group
+@end example
+
+Of the variables listed above, four have values that are single file
+names, and three have values that are lists of file names.  These seven
+have variants that get just the file's directory name or just the file
+name within the directory.  The variant variables' names are formed by
+appending @samp{D} or @samp{F}, respectively.  These variants are
+semi-obsolete in GNU @code{make} since the functions @code{dir} and
+@code{notdir} can be used to get a similar effect (@pxref{File Name
+Functions, , Functions for File Names}).  Note, however, that the
+@samp{D} variants all omit the trailing slash which always appears in
+the output of the @code{dir} function.  Here is a table of the variants:
+
+@table @samp
+@vindex $(@@D)
+@vindex @@D @r{(automatic variable)}
+@item $(@@D)
+The directory part of the file name of the target, with the trailing
+slash removed.  If the value of @samp{$@@} is @file{dir/foo.o} then
+@samp{$(@@D)} is @file{dir}.  This value is @file{.} if @samp{$@@} does
+not contain a slash.
+
+@vindex $(@@F)
+@vindex @@F @r{(automatic variable)}
+@item $(@@F)
+The file-within-directory part of the file name of the target.  If the
+value of @samp{$@@} is @file{dir/foo.o} then @samp{$(@@F)} is
+@file{foo.o}.  @samp{$(@@F)} is equivalent to @samp{$(notdir $@@)}.
+
+@vindex $(*D)
+@vindex *D @r{(automatic variable)}
+@item $(*D)
+@vindex $(*F)
+@vindex *F @r{(automatic variable)}
+@itemx $(*F)
+The directory part and the file-within-directory
+part of the stem; @file{dir} and @file{foo} in this example.
+
+@vindex $(%D)
+@vindex %D @r{(automatic variable)}
+@item $(%D)
+@vindex $(%F)
+@vindex %F @r{(automatic variable)}
+@itemx $(%F)
+The directory part and the file-within-directory part of the target
+archive member name.  This makes sense only for archive member targets
+of the form @file{@var{archive}(@var{member})} and is useful only when
+@var{member} may contain a directory name.  (@xref{Archive Members,
+,Archive Members as Targets}.)
+
+@vindex $(<D)
+@vindex <D @r{(automatic variable)}
+@item $(<D)
+@vindex $(<F)
+@vindex <F @r{(automatic variable)}
+@itemx $(<F)
+The directory part and the file-within-directory
+part of the first prerequisite.
+
+@vindex $(^D)
+@vindex ^D @r{(automatic variable)}
+@item $(^D)
+@vindex $(^F)
+@vindex ^F @r{(automatic variable)}
+@itemx $(^F)
+Lists of the directory parts and the file-within-directory
+parts of all prerequisites.
+
+@vindex $(?D)
+@vindex ?D @r{(automatic variable)}
+@item $(?D)
+@vindex $(?F)
+@vindex ?F @r{(automatic variable)}
+@itemx $(?F)
+Lists of the directory parts and the file-within-directory parts of
+all prerequisites that are newer than the target.
+@end table
+
+Note that we use a special stylistic convention when we talk about these
+automatic variables; we write ``the value of @samp{$<}'', rather than
+@w{``the variable @code{<}''} as we would write for ordinary variables
+such as @code{objects} and @code{CFLAGS}.  We think this convention
+looks more natural in this special case.  Please do not assume it has a
+deep significance; @samp{$<} refers to the variable named @code{<} just
+as @samp{$(CFLAGS)} refers to the variable named @code{CFLAGS}.
+You could just as well use @samp{$(<)} in place of @samp{$<}.
+
+@node Pattern Match, Match-Anything Rules, Automatic, Pattern Rules
+@subsection How Patterns Match
+
+@cindex stem
+A target pattern is composed of a @samp{%} between a prefix and a suffix,
+either or both of which may be empty.  The pattern matches a file name only
+if the file name starts with the prefix and ends with the suffix, without
+overlap.  The text between the prefix and the suffix is called the
+@dfn{stem}.  Thus, when the pattern @samp{%.o} matches the file name
+@file{test.o}, the stem is @samp{test}.  The pattern rule prerequisites are
+turned into actual file names by substituting the stem for the character
+@samp{%}.  Thus, if in the same example one of the prerequisites is written
+as @samp{%.c}, it expands to @samp{test.c}.@refill
+
+When the target pattern does not contain a slash (and it usually does
+not), directory names in the file names are removed from the file name
+before it is compared with the target prefix and suffix.  After the
+comparison of the file name to the target pattern, the directory
+names, along with the slash that ends them, are added on to the
+prerequisite file names generated from the pattern rule's prerequisite
+patterns and the file name. The directories are ignored only for the
+purpose of finding an implicit rule to use, not in the application of
+that rule.  Thus, @samp{e%t} matches the file name @file{src/eat},
+with @samp{src/a} as the stem.  When prerequisites are turned into file
+names, the directories from the stem are added at the front, while the
+rest of the stem is substituted for the @samp{%}.  The stem
+@samp{src/a} with a prerequisite pattern @samp{c%r} gives the file name
+@file{src/car}.@refill
+
+@node Match-Anything Rules, Canceling Rules, Pattern Match, Pattern Rules
+@subsection Match-Anything Pattern Rules
+
+@cindex match-anything rule
+@cindex terminal rule
+When a pattern rule's target is just @samp{%}, it matches any file name
+whatever.  We call these rules @dfn{match-anything} rules.  They are very
+useful, but it can take a lot of time for @code{make} to think about them,
+because it must consider every such rule for each file name listed either
+as a target or as a prerequisite.
+
+Suppose the makefile mentions @file{foo.c}.  For this target, @code{make}
+would have to consider making it by linking an object file @file{foo.c.o},
+or by C compilation-and-linking in one step from @file{foo.c.c}, or by
+Pascal compilation-and-linking from @file{foo.c.p}, and many other
+possibilities.
+
+We know these possibilities are ridiculous since @file{foo.c} is a C source
+file, not an executable.  If @code{make} did consider these possibilities,
+it would ultimately reject them, because files such as @file{foo.c.o} and
+@file{foo.c.p} would not exist.  But these possibilities are so
+numerous that @code{make} would run very slowly if it had to consider
+them.@refill
+
+To gain speed, we have put various constraints on the way @code{make}
+considers match-anything rules.  There are two different constraints that
+can be applied, and each time you define a match-anything rule you must
+choose one or the other for that rule.
+
+One choice is to mark the match-anything rule as @dfn{terminal} by defining
+it with a double colon.  When a rule is terminal, it does not apply unless
+its prerequisites actually exist.  Prerequisites that could be made with
+other implicit rules are not good enough.  In other words, no further
+chaining is allowed beyond a terminal rule.
+
+For example, the built-in implicit rules for extracting sources from RCS
+and SCCS files are terminal; as a result, if the file @file{foo.c,v} does
+not exist, @code{make} will not even consider trying to make it as an
+intermediate file from @file{foo.c,v.o} or from @file{RCS/SCCS/s.foo.c,v}.
+RCS and SCCS files are generally ultimate source files, which should not be
+remade from any other files; therefore, @code{make} can save time by not
+looking for ways to remake them.@refill
+
+If you do not mark the match-anything rule as terminal, then it is
+nonterminal.  A nonterminal match-anything rule cannot apply to a file name
+that indicates a specific type of data.  A file name indicates a specific
+type of data if some non-match-anything implicit rule target matches it.
+
+For example, the file name @file{foo.c} matches the target for the pattern
+rule @samp{%.c : %.y} (the rule to run Yacc).  Regardless of whether this
+rule is actually applicable (which happens only if there is a file
+@file{foo.y}), the fact that its target matches is enough to prevent
+consideration of any nonterminal match-anything rules for the file
+@file{foo.c}.  Thus, @code{make} will not even consider trying to make
+@file{foo.c} as an executable file from @file{foo.c.o}, @file{foo.c.c},
+@file{foo.c.p}, etc.@refill
+
+The motivation for this constraint is that nonterminal match-anything
+rules are used for making files containing specific types of data (such as
+executable files) and a file name with a recognized suffix indicates some
+other specific type of data (such as a C source file).
+
+Special built-in dummy pattern rules are provided solely to recognize
+certain file names so that nonterminal match-anything rules will not be
+considered.  These dummy rules have no prerequisites and no commands, and
+they are ignored for all other purposes.  For example, the built-in
+implicit rule
+
+@example
+%.p :
+@end example
+
+@noindent
+exists to make sure that Pascal source files such as @file{foo.p} match a
+specific target pattern and thereby prevent time from being wasted looking
+for @file{foo.p.o} or @file{foo.p.c}.
+
+Dummy pattern rules such as the one for @samp{%.p} are made for every
+suffix listed as valid for use in suffix rules (@pxref{Suffix Rules, ,Old-Fashioned Suffix Rules}).
+
+@node Canceling Rules,  , Match-Anything Rules, Pattern Rules
+@subsection Canceling Implicit Rules
+
+You can override a built-in implicit rule (or one you have defined
+yourself) by defining a new pattern rule with the same target and
+prerequisites, but different commands.  When the new rule is defined, the
+built-in one is replaced.  The new rule's position in the sequence of
+implicit rules is determined by where you write the new rule.
+
+You can cancel a built-in implicit rule by defining a pattern rule with the
+same target and prerequisites, but no commands.  For example, the following
+would cancel the rule that runs the assembler:
+
+@example
+%.o : %.s
+@end example
+
+@node Last Resort, Suffix Rules, Pattern Rules, Implicit Rules
+@section Defining Last-Resort Default Rules
+@cindex last-resort default rules
+@cindex default rules, last-resort
+
+You can define a last-resort implicit rule by writing a terminal
+match-anything pattern rule with no prerequisites (@pxref{Match-Anything
+Rules}).  This is just like any other pattern rule; the only thing
+special about it is that it will match any target.  So such a rule's
+commands are used for all targets and prerequisites that have no commands
+of their own and for which no other implicit rule applies.
+
+For example, when testing a makefile, you might not care if the source
+files contain real data, only that they exist.  Then you might do this:
+
+@example
+%::
+        touch $@@
+@end example
+
+@noindent
+to cause all the source files needed (as prerequisites) to be created
+automatically.
+
+@findex .DEFAULT
+You can instead define commands to be used for targets for which there
+are no rules at all, even ones which don't specify commands.  You do
+this by writing a rule for the target @code{.DEFAULT}.  Such a rule's
+commands are used for all prerequisites which do not appear as targets in
+any explicit rule, and for which no implicit rule applies.  Naturally,
+there is no @code{.DEFAULT} rule unless you write one.
+
+If you use @code{.DEFAULT} with no commands or prerequisites:
+
+@example
+.DEFAULT:
+@end example
+
+@noindent
+the commands previously stored for @code{.DEFAULT} are cleared.
+Then @code{make} acts as if you had never defined @code{.DEFAULT} at all.
+
+If you do not want a target to get the commands from a match-anything
+pattern rule or @code{.DEFAULT}, but you also do not want any commands
+to be run for the target, you can give it empty commands (@pxref{Empty
+Commands, ,Defining Empty Commands}).@refill
+
+You can use a last-resort rule to override part of another makefile.
+@xref{Overriding Makefiles, , Overriding Part of Another Makefile}.
+
+@node Suffix Rules, Implicit Rule Search, Last Resort, Implicit Rules
+@section Old-Fashioned Suffix Rules
+@cindex old-fashioned suffix rules
+@cindex suffix rule
+
+@dfn{Suffix rules} are the old-fashioned way of defining implicit rules for
+@code{make}.  Suffix rules are obsolete because pattern rules are more
+general and clearer.  They are supported in GNU @code{make} for
+compatibility with old makefiles.  They come in two kinds:
+@dfn{double-suffix} and @dfn{single-suffix}.@refill
+
+A double-suffix rule is defined by a pair of suffixes: the target suffix
+and the source suffix.  It matches any file whose name ends with the
+target suffix.  The corresponding implicit prerequisite is made by
+replacing the target suffix with the source suffix in the file name.  A
+two-suffix rule whose target and source suffixes are @samp{.o} and
+@samp{.c} is equivalent to the pattern rule @samp{%.o : %.c}.
+
+A single-suffix rule is defined by a single suffix, which is the source
+suffix.  It matches any file name, and the corresponding implicit
+prerequisite name is made by appending the source suffix.  A single-suffix
+rule whose source suffix is @samp{.c} is equivalent to the pattern rule
+@samp{% : %.c}.
+
+Suffix rule definitions are recognized by comparing each rule's target
+against a defined list of known suffixes.  When @code{make} sees a rule
+whose target is a known suffix, this rule is considered a single-suffix
+rule.  When @code{make} sees a rule whose target is two known suffixes
+concatenated, this rule is taken as a double-suffix rule.
+
+For example, @samp{.c} and @samp{.o} are both on the default list of
+known suffixes.  Therefore, if you define a rule whose target is
+@samp{.c.o}, @code{make} takes it to be a double-suffix rule with source
+suffix @samp{.c} and target suffix @samp{.o}.  Here is the old-fashioned
+way to define the rule for compiling a C source file:@refill
+
+@example
+.c.o:
+        $(CC) -c $(CFLAGS) $(CPPFLAGS) -o $@@ $<
+@end example
+
+Suffix rules cannot have any prerequisites of their own.  If they have any,
+they are treated as normal files with funny names, not as suffix rules.
+Thus, the rule:
+
+@example
+.c.o: foo.h
+        $(CC) -c $(CFLAGS) $(CPPFLAGS) -o $@@ $<
+@end example
+
+@noindent
+tells how to make the file @file{.c.o} from the prerequisite file
+@file{foo.h}, and is not at all like the pattern rule:
+
+@example
+%.o: %.c foo.h
+        $(CC) -c $(CFLAGS) $(CPPFLAGS) -o $@@ $<
+@end example
+
+@noindent
+which tells how to make @samp{.o} files from @samp{.c} files, and makes all
+@samp{.o} files using this pattern rule also depend on @file{foo.h}.
+
+Suffix rules with no commands are also meaningless.  They do not remove
+previous rules as do pattern rules with no commands (@pxref{Canceling
+Rules, , Canceling Implicit Rules}).  They simply enter the suffix or pair of suffixes concatenated as
+a target in the data base.@refill
+
+@findex .SUFFIXES
+The known suffixes are simply the names of the prerequisites of the special
+target @code{.SUFFIXES}.  You can add your own suffixes by writing a rule
+for @code{.SUFFIXES} that adds more prerequisites, as in:
+
+@example
+.SUFFIXES: .hack .win
+@end example
+
+@noindent
+which adds @samp{.hack} and @samp{.win} to the end of the list of suffixes.
+
+If you wish to eliminate the default known suffixes instead of just adding
+to them, write a rule for @code{.SUFFIXES} with no prerequisites.  By
+special dispensation, this eliminates all existing prerequisites of
+@code{.SUFFIXES}.  You can then write another rule to add the suffixes you
+want.  For example,
+
+@example
+@group
+.SUFFIXES:            # @r{Delete the default suffixes}
+.SUFFIXES: .c .o .h   # @r{Define our suffix list}
+@end group
+@end example
+
+The @samp{-r} or @samp{--no-builtin-rules} flag causes the default
+list of suffixes to be empty.
+
+@vindex SUFFIXES
+The variable @code{SUFFIXES} is defined to the default list of suffixes
+before @code{make} reads any makefiles.  You can change the list of suffixes
+with a rule for the special target @code{.SUFFIXES}, but that does not alter
+this variable.
+
+@node Implicit Rule Search,  , Suffix Rules, Implicit Rules
+@section Implicit Rule Search Algorithm
+@cindex implicit rule, search algorithm
+@cindex search algorithm, implicit rule
+
+Here is the procedure @code{make} uses for searching for an implicit rule
+for a target @var{t}.  This procedure is followed for each double-colon
+rule with no commands, for each target of ordinary rules none of which have
+commands, and for each prerequisite that is not the target of any rule.  It
+is also followed recursively for prerequisites that come from implicit
+rules, in the search for a chain of rules.
+
+Suffix rules are not mentioned in this algorithm because suffix rules are
+converted to equivalent pattern rules once the makefiles have been read in.
+
+For an archive member target of the form
+@samp{@var{archive}(@var{member})}, the following algorithm is run
+twice, first using the entire target name @var{t}, and second using
+@samp{(@var{member})} as the target @var{t} if the first run found no
+rule.@refill
+
+@enumerate
+@item
+Split @var{t} into a directory part, called @var{d}, and the rest,
+called @var{n}.  For example, if @var{t} is @samp{src/foo.o}, then
+@var{d} is @samp{src/} and @var{n} is @samp{foo.o}.@refill
+
+@item
+Make a list of all the pattern rules one of whose targets matches
+@var{t} or @var{n}.  If the target pattern contains a slash, it is
+matched against @var{t}; otherwise, against @var{n}.
+
+@item
+If any rule in that list is @emph{not} a match-anything rule, then
+remove all nonterminal match-anything rules from the list.
+
+@item
+Remove from the list all rules with no commands.
+
+@item
+For each pattern rule in the list:
+
+@enumerate a
+@item
+Find the stem @var{s}, which is the nonempty part of @var{t} or @var{n}
+matched by the @samp{%} in the target pattern.@refill
+
+@item
+Compute the prerequisite names by substituting @var{s} for @samp{%}; if
+the target pattern does not contain a slash, append @var{d} to
+the front of each prerequisite name.@refill
+
+@item
+Test whether all the prerequisites exist or ought to exist.  (If a
+file name is mentioned in the makefile as a target or as an explicit
+prerequisite, then we say it ought to exist.)
+
+If all prerequisites exist or ought to exist, or there are no prerequisites,
+then this rule applies.
+@end enumerate
+
+@item
+If no pattern rule has been found so far, try harder.
+For each pattern rule in the list:
+
+@enumerate a
+@item
+If the rule is terminal, ignore it and go on to the next rule.
+
+@item
+Compute the prerequisite names as before.
+
+@item
+Test whether all the prerequisites exist or ought to exist.
+
+@item
+For each prerequisite that does not exist, follow this algorithm
+recursively to see if the prerequisite can be made by an implicit
+rule.
+
+@item
+If all prerequisites exist, ought to exist, or can be
+made by implicit rules, then this rule applies.
+@end enumerate
+
+@item
+If no implicit rule applies, the rule for @code{.DEFAULT}, if any,
+applies.  In that case, give @var{t} the same commands that
+@code{.DEFAULT} has.  Otherwise, there are no commands for @var{t}.
+@end enumerate
+
+Once a rule that applies has been found, for each target pattern of the
+rule other than the one that matched @var{t} or @var{n}, the @samp{%} in
+the pattern is replaced with @var{s} and the resultant file name is stored
+until the commands to remake the target file @var{t} are executed.  After
+these commands are executed, each of these stored file names are entered
+into the data base and marked as having been updated and having the same
+update status as the file @var{t}.
+
+When the commands of a pattern rule are executed for @var{t}, the automatic
+variables are set corresponding to the target and prerequisites.
+@xref{Automatic, ,Automatic Variables}.
+
+@node Archives, Features, Implicit Rules, Top
+@chapter Using @code{make} to Update Archive Files
+@cindex archive
+
+@dfn{Archive files} are files containing named subfiles called
+@dfn{members}; they are maintained with the program @code{ar} and their
+main use is as subroutine libraries for linking.
+
+@menu
+* Archive Members::             Archive members as targets.
+* Archive Update::              The implicit rule for archive member targets.
+* Archive Pitfalls::            Dangers to watch out for when using archives.
+* Archive Suffix Rules::        You can write a special kind of suffix rule
+                                  for updating archives.
+@end menu
+
+@node Archive Members, Archive Update, Archives, Archives
+@section Archive Members as Targets
+@cindex archive member targets
+
+An individual member of an archive file can be used as a target or
+prerequisite in @code{make}.  You specify the member named @var{member} in
+archive file @var{archive} as follows:
+
+@example
+@var{archive}(@var{member})
+@end example
+
+@noindent
+This construct is available only in targets and prerequisites, not in
+commands!  Most programs that you might use in commands do not support this
+syntax and cannot act directly on archive members.  Only @code{ar} and
+other programs specifically designed to operate on archives can do so.
+Therefore, valid commands to update an archive member target probably must
+use @code{ar}.  For example, this rule says to create a member
+@file{hack.o} in archive @file{foolib} by copying the file @file{hack.o}:
+
+@example
+foolib(hack.o) : hack.o
+        ar cr foolib hack.o
+@end example
+
+In fact, nearly all archive member targets are updated in just this way
+and there is an implicit rule to do it for you.  @strong{Note:} The
+@samp{c} flag to @code{ar} is required if the archive file does not
+already exist.
+
+To specify several members in the same archive, you can write all the
+member names together between the parentheses.  For example:
+
+@example
+foolib(hack.o kludge.o)
+@end example
+
+@noindent
+is equivalent to:
+
+@example
+foolib(hack.o) foolib(kludge.o)
+@end example
+
+@cindex wildcard, in archive member
+You can also use shell-style wildcards in an archive member reference.
+@xref{Wildcards, ,Using Wildcard Characters in File Names}.  For
+example, @w{@samp{foolib(*.o)}} expands to all existing members of the
+@file{foolib} archive whose names end in @samp{.o}; perhaps
+@samp{@w{foolib(hack.o)} @w{foolib(kludge.o)}}.
+
+@node Archive Update, Archive Pitfalls, Archive Members, Archives
+@section Implicit Rule for Archive Member Targets
+
+Recall that a target that looks like @file{@var{a}(@var{m})} stands for the
+member named @var{m} in the archive file @var{a}.
+
+When @code{make} looks for an implicit rule for such a target, as a special
+feature it considers implicit rules that match @file{(@var{m})}, as well as
+those that match the actual target @file{@var{a}(@var{m})}.
+
+This causes one special rule whose target is @file{(%)} to match.  This
+rule updates the target @file{@var{a}(@var{m})} by copying the file @var{m}
+into the archive.  For example, it will update the archive member target
+@file{foo.a(bar.o)} by copying the @emph{file} @file{bar.o} into the
+archive @file{foo.a} as a @emph{member} named @file{bar.o}.
+
+When this rule is chained with others, the result is very powerful.
+Thus, @samp{make "foo.a(bar.o)"} (the quotes are needed to protect the
+@samp{(} and @samp{)} from being interpreted specially by the shell) in
+the presence of a file @file{bar.c} is enough to cause the following
+commands to be run, even without a makefile:
+
+@example
+cc -c bar.c -o bar.o
+ar r foo.a bar.o
+rm -f bar.o
+@end example
+
+@noindent
+Here @code{make} has envisioned the file @file{bar.o} as an intermediate
+file.  @xref{Chained Rules, ,Chains of Implicit Rules}.
+
+Implicit rules such as this one are written using the automatic variable
+@samp{$%}.  @xref{Automatic, ,Automatic Variables}.
+
+An archive member name in an archive cannot contain a directory name, but
+it may be useful in a makefile to pretend that it does.  If you write an
+archive member target @file{foo.a(dir/file.o)}, @code{make} will perform
+automatic updating with this command:
+
+@example
+ar r foo.a dir/file.o
+@end example
+
+@noindent
+which has the effect of copying the file @file{dir/file.o} into a member
+named @file{file.o}.  In connection with such usage, the automatic variables
+@code{%D} and @code{%F} may be useful.
+
+@menu
+* Archive Symbols::             How to update archive symbol directories.
+@end menu
+
+@node Archive Symbols,  , Archive Update, Archive Update
+@subsection Updating Archive Symbol Directories
+@cindex @code{__.SYMDEF}
+@cindex updating archive symbol directories
+@cindex archive symbol directory updating
+@cindex symbol directories, updating archive
+@cindex directories, updating archive symbol
+
+An archive file that is used as a library usually contains a special member
+named @file{__.SYMDEF} that contains a directory of the external symbol
+names defined by all the other members.  After you update any other
+members, you need to update @file{__.SYMDEF} so that it will summarize the
+other members properly.  This is done by running the @code{ranlib} program:
+
+@example
+ranlib @var{archivefile}
+@end example
+
+Normally you would put this command in the rule for the archive file,
+and make all the members of the archive file prerequisites of that rule.
+For example,
+
+@example
+libfoo.a: libfoo.a(x.o) libfoo.a(y.o) @dots{}
+        ranlib libfoo.a
+@end example
+
+@noindent
+The effect of this is to update archive members @file{x.o}, @file{y.o},
+etc., and then update the symbol directory member @file{__.SYMDEF} by
+running @code{ranlib}.  The rules for updating the members are not shown
+here; most likely you can omit them and use the implicit rule which copies
+files into the archive, as described in the preceding section.
+
+This is not necessary when using the GNU @code{ar} program, which
+updates the @file{__.SYMDEF} member automatically.
+
+@node Archive Pitfalls, Archive Suffix Rules, Archive Update, Archives
+@section Dangers When Using Archives
+@cindex archive, and parallel execution
+@cindex parallel execution, and archive update
+@cindex archive, and @code{-j}
+@cindex @code{-j}, and archive update
+
+It is important to be careful when using parallel execution (the
+@code{-j} switch; @pxref{Parallel, ,Parallel Execution}) and archives.
+If multiple @code{ar} commands run at the same time on the same archive
+file, they will not know about each other and can corrupt the file.
+
+Possibly a future version of @code{make} will provide a mechanism to
+circumvent this problem by serializing all commands that operate on the
+same archive file.  But for the time being, you must either write your
+makefiles to avoid this problem in some other way, or not use @code{-j}.
+
+@node Archive Suffix Rules,  , Archive Pitfalls, Archives
+@section Suffix Rules for Archive Files
+@cindex suffix rule, for archive
+@cindex archive, suffix rule for
+@cindex library archive, suffix rule for
+@cindex @code{.a} (archives)
+
+You can write a special kind of suffix rule for dealing with archive
+files.  @xref{Suffix Rules}, for a full explanation of suffix rules.
+Archive suffix rules are obsolete in GNU @code{make}, because pattern
+rules for archives are a more general mechanism (@pxref{Archive
+Update}).  But they are retained for compatibility with other
+@code{make}s.
+
+To write a suffix rule for archives, you simply write a suffix rule
+using the target suffix @samp{.a} (the usual suffix for archive files).
+For example, here is the old-fashioned suffix rule to update a library
+archive from C source files:
+
+@example
+@group
+.c.a:
+        $(CC) $(CFLAGS) $(CPPFLAGS) -c $< -o $*.o
+        $(AR) r $@@ $*.o
+        $(RM) $*.o
+@end group
+@end example
+
+@noindent
+This works just as if you had written the pattern rule:
+
+@example
+@group
+(%.o): %.c
+        $(CC) $(CFLAGS) $(CPPFLAGS) -c $< -o $*.o
+        $(AR) r $@@ $*.o
+        $(RM) $*.o
+@end group
+@end example
+
+In fact, this is just what @code{make} does when it sees a suffix rule
+with @samp{.a} as the target suffix.  Any double-suffix rule
+@w{@samp{.@var{x}.a}} is converted to a pattern rule with the target
+pattern @samp{(%.o)} and a prerequisite pattern of @samp{%.@var{x}}.
+
+Since you might want to use @samp{.a} as the suffix for some other kind
+of file, @code{make} also converts archive suffix rules to pattern rules
+in the normal way (@pxref{Suffix Rules}).  Thus a double-suffix rule
+@w{@samp{.@var{x}.a}} produces two pattern rules: @samp{@w{(%.o):}
+@w{%.@var{x}}} and @samp{@w{%.a}: @w{%.@var{x}}}.@refill
+
+@node Features, Missing, Archives, Top
+@chapter Features of GNU @code{make}
+@cindex features of GNU @code{make}
+@cindex portability
+@cindex compatibility
+
+Here is a summary of the features of GNU @code{make}, for comparison
+with and credit to other versions of @code{make}.  We consider the
+features of @code{make} in 4.2 BSD systems as a baseline.  If you are
+concerned with writing portable makefiles, you should not use the
+features of @code{make} listed here, nor the ones in @ref{Missing}.
+
+Many features come from the version of @code{make} in System V.
+
+@itemize @bullet
+@item
+The @code{VPATH} variable and its special meaning.
+@xref{Directory Search, , Searching Directories for Prerequisites}.
+This feature exists in System V @code{make}, but is undocumented.
+It is documented in 4.3 BSD @code{make} (which says it mimics System V's
+@code{VPATH} feature).@refill
+
+@item
+Included makefiles.  @xref{Include, ,Including Other Makefiles}.
+Allowing multiple files to be included with a single directive is a GNU
+extension.
+
+@item
+Variables are read from and communicated via the environment.
+@xref{Environment, ,Variables from the Environment}.
+
+@item
+Options passed through the variable @code{MAKEFLAGS} to recursive
+invocations of @code{make}.
+@xref{Options/Recursion, ,Communicating Options to a Sub-@code{make}}.
+
+@item
+The automatic variable @code{$%} is set to the member name
+in an archive reference.  @xref{Automatic, ,Automatic Variables}.
+
+@item
+The automatic variables @code{$@@}, @code{$*}, @code{$<}, @code{$%},
+and @code{$?} have corresponding forms like @code{$(@@F)} and
+@code{$(@@D)}.  We have generalized this to @code{$^} as an obvious
+extension.  @xref{Automatic, ,Automatic Variables}.@refill
+
+@item
+Substitution variable references.
+@xref{Reference, ,Basics of Variable References}.
+
+@item
+The command-line options @samp{-b} and @samp{-m}, accepted and
+ignored.  In System V @code{make}, these options actually do something.
+
+@item
+Execution of recursive commands to run @code{make} via the variable
+@code{MAKE} even if @samp{-n}, @samp{-q} or @samp{-t} is specified.
+@xref{Recursion, ,Recursive Use of @code{make}}.
+
+@item
+Support for suffix @samp{.a} in suffix rules.  @xref{Archive Suffix
+Rules}.  This feature is obsolete in GNU @code{make}, because the
+general feature of rule chaining (@pxref{Chained Rules, ,Chains of
+Implicit Rules}) allows one pattern rule for installing members in an
+archive (@pxref{Archive Update}) to be sufficient.
+
+@item
+The arrangement of lines and backslash-newline combinations in
+commands is retained when the commands are printed, so they appear as
+they do in the makefile, except for the stripping of initial
+whitespace.
+@end itemize
+
+The following features were inspired by various other versions of
+@code{make}.  In some cases it is unclear exactly which versions inspired
+which others.
+
+@itemize @bullet
+@item
+Pattern rules using @samp{%}.
+This has been implemented in several versions of @code{make}.
+We're not sure who invented it first, but it's been spread around a bit.
+@xref{Pattern Rules, ,Defining and Redefining Pattern Rules}.@refill
+
+@item
+Rule chaining and implicit intermediate files.
+This was implemented by Stu Feldman in his version of @code{make}
+for AT&T Eighth Edition Research Unix, and later by Andrew Hume of
+AT&T Bell Labs in his @code{mk} program (where he terms it
+``transitive closure'').  We do not really know if
+we got this from either of them or thought it up ourselves at the
+same time.  @xref{Chained Rules, ,Chains of Implicit Rules}.
+
+@item
+The automatic variable @code{$^} containing a list of all prerequisites
+of the current target.  We did not invent this, but we have no idea who
+did.  @xref{Automatic, ,Automatic Variables}.  The automatic variable
+@code{$+} is a simple extension of @code{$^}.
+
+@item
+The ``what if'' flag (@samp{-W} in GNU @code{make}) was (as far as we know)
+invented by Andrew Hume in @code{mk}.
+@xref{Instead of Execution, ,Instead of Executing the Commands}.
+
+@item
+The concept of doing several things at once (parallelism) exists in
+many incarnations of @code{make} and similar programs, though not in the
+System V or BSD implementations.  @xref{Execution, ,Command Execution}.
+
+@item
+Modified variable references using pattern substitution come from
+SunOS 4.  @xref{Reference, ,Basics of Variable References}.
+This functionality was provided in GNU @code{make} by the
+@code{patsubst} function before the alternate syntax was implemented
+for compatibility with SunOS 4.  It is not altogether clear who
+inspired whom, since GNU @code{make} had @code{patsubst} before SunOS
+4 was released.@refill
+
+@item
+The special significance of @samp{+} characters preceding command lines
+(@pxref{Instead of Execution, ,Instead of Executing the Commands}) is
+mandated by
+@cite{IEEE Standard 1003.2-1992} (POSIX.2).
+
+@item
+The @samp{+=} syntax to append to the value of a variable comes from SunOS
+4 @code{make}.  @xref{Appending, , Appending More Text to Variables}.
+
+@item
+The syntax @w{@samp{@var{archive}(@var{mem1} @var{mem2}@dots{})}} to list
+multiple members in a single archive file comes from SunOS 4 @code{make}.
+@xref{Archive Members}.
+
+@item
+The @code{-include} directive to include makefiles with no error for a
+nonexistent file comes from SunOS 4 @code{make}.  (But note that SunOS 4
+@code{make} does not allow multiple makefiles to be specified in one
+@code{-include} directive.)  The same feature appears with the name
+@code{sinclude} in SGI @code{make} and perhaps others.
+@end itemize
+
+The remaining features are inventions new in GNU @code{make}:
+
+@itemize @bullet
+@item
+Use the @samp{-v} or @samp{--version} option to print version and
+copyright information.
+
+@item
+Use the @samp{-h} or @samp{--help} option to summarize the options to
+@code{make}.
+
+@item
+Simply-expanded variables.  @xref{Flavors, ,The Two Flavors of Variables}.
+
+@item
+Pass command-line variable assignments automatically through the
+variable @code{MAKE} to recursive @code{make} invocations.
+@xref{Recursion, ,Recursive Use of @code{make}}.
+
+@item
+Use the @samp{-C} or @samp{--directory} command option to change
+directory.  @xref{Options Summary, ,Summary of Options}.
+
+@item
+Make verbatim variable definitions with @code{define}.
+@xref{Defining, ,Defining Variables Verbatim}.
+
+@item
+Declare phony targets with the special target @code{.PHONY}.
+
+Andrew Hume of AT&T Bell Labs implemented a similar feature with a
+different syntax in his @code{mk} program.  This seems to be a case of
+parallel discovery.  @xref{Phony Targets, ,Phony Targets}.
+
+@item
+Manipulate text by calling functions.
+@xref{Functions, ,Functions for Transforming Text}.
+
+@item
+Use the @samp{-o} or @samp{--old-file}
+option to pretend a file's modification-time is old.
+@xref{Avoiding Compilation, ,Avoiding Recompilation of Some Files}.
+
+@item
+Conditional execution.
+
+This feature has been implemented numerous times in various versions
+of @code{make}; it seems a natural extension derived from the features
+of the C preprocessor and similar macro languages and is not a
+revolutionary concept.  @xref{Conditionals, ,Conditional Parts of Makefiles}.
+
+@item
+Specify a search path for included makefiles.
+@xref{Include, ,Including Other Makefiles}.
+
+@item
+Specify extra makefiles to read with an environment variable.
+@xref{MAKEFILES Variable, ,The Variable @code{MAKEFILES}}.
+
+@item
+Strip leading sequences of @samp{./} from file names, so that
+@file{./@var{file}} and @file{@var{file}} are considered to be the
+same file.@refill
+
+@item
+Use a special search method for library prerequisites written in the
+form @samp{-l@var{name}}.
+@xref{Libraries/Search, ,Directory Search for Link Libraries}.
+
+@item
+Allow suffixes for suffix rules
+(@pxref{Suffix Rules, ,Old-Fashioned Suffix Rules}) to contain any
+characters.  In other versions of @code{make}, they must begin with
+@samp{.} and not contain any @samp{/} characters.
+
+@item
+Keep track of the current level of @code{make} recursion using the
+variable @code{MAKELEVEL}.  @xref{Recursion, ,Recursive Use of @code{make}}.
+
+@item
+Provide any goals given on the command line in the variable
+@code{MAKECMDGOALS}.  @xref{Goals, ,Arguments to Specify the Goals}.
+
+@item
+Specify static pattern rules.  @xref{Static Pattern, ,Static Pattern Rules}.
+
+@item
+Provide selective @code{vpath} search.
+@xref{Directory Search, ,Searching Directories for Prerequisites}.
+
+@item
+Provide computed variable references.
+@xref{Reference, ,Basics of Variable References}.
+
+@item
+Update makefiles.  @xref{Remaking Makefiles, ,How Makefiles Are Remade}.
+System V @code{make} has a very, very limited form of this
+functionality in that it will check out SCCS files for makefiles.
+
+@item
+Various new built-in implicit rules.
+@xref{Catalogue of Rules, ,Catalogue of Implicit Rules}.
+
+@item
+The built-in variable @samp{MAKE_VERSION} gives the version number of
+@code{make}.
+@end itemize
+
+@node Missing, Makefile Conventions, Features, Top
+@chapter Incompatibilities and Missing Features
+@cindex incompatibilities
+@cindex missing features
+@cindex features, missing
+
+The @code{make} programs in various other systems support a few features
+that are not implemented in GNU @code{make}.  The POSIX.2 standard
+(@cite{IEEE Standard 1003.2-1992}) which specifies @code{make} does not
+require any of these features.@refill
+
+@itemize @bullet
+@item
+A target of the form @samp{@var{file}((@var{entry}))} stands for a member
+of archive file @var{file}.  The member is chosen, not by name, but by
+being an object file which defines the linker symbol @var{entry}.@refill
+
+This feature was not put into GNU @code{make} because of the
+nonmodularity of putting knowledge into @code{make} of the internal
+format of archive file symbol tables.
+@xref{Archive Symbols, ,Updating Archive Symbol Directories}.
+
+@item
+Suffixes (used in suffix rules) that end with the character @samp{~}
+have a special meaning to System V @code{make};
+they refer to the SCCS file that corresponds
+to the file one would get without the @samp{~}.  For example, the
+suffix rule @samp{.c~.o} would make the file @file{@var{n}.o} from
+the SCCS file @file{s.@var{n}.c}.  For complete coverage, a whole
+series of such suffix rules is required.
+@xref{Suffix Rules, ,Old-Fashioned Suffix Rules}.
+
+In GNU @code{make}, this entire series of cases is handled by two
+pattern rules for extraction from SCCS, in combination with the
+general feature of rule chaining.
+@xref{Chained Rules, ,Chains of Implicit Rules}.
+
+@item
+In System V @code{make}, the string @samp{$$@@} has the strange meaning
+that, in the prerequisites of a rule with multiple targets, it stands
+for the particular target that is being processed.
+
+This is not defined in GNU @code{make} because @samp{$$} should always
+stand for an ordinary @samp{$}.
+
+It is possible to get portions of this functionality through the use of
+static pattern rules (@pxref{Static Pattern, ,Static Pattern Rules}).
+The System V @code{make} rule:
+
+@example
+$(targets): $$@@.o lib.a
+@end example
+
+@noindent
+can be replaced with the GNU @code{make} static pattern rule:
+
+@example
+$(targets): %: %.o lib.a
+@end example
+
+@item
+In System V and 4.3 BSD @code{make}, files found by @code{VPATH} search
+(@pxref{Directory Search, ,Searching Directories for Prerequisites}) have their names changed inside command
+strings.  We feel it is much cleaner to always use automatic variables
+and thus make this feature obsolete.@refill
+
+@item
+In some Unix @code{make}s, the automatic variable @code{$*} appearing in
+the prerequisites of a rule has the amazingly strange ``feature'' of
+expanding to the full name of the @emph{target of that rule}.  We cannot
+imagine what went on in the minds of Unix @code{make} developers to do
+this; it is utterly inconsistent with the normal definition of @code{$*}.
+@vindex * @r{(automatic variable), unsupported bizarre usage}
+
+@item
+In some Unix @code{make}s, implicit rule search
+(@pxref{Implicit Rules, ,Using Implicit Rules}) is apparently done for
+@emph{all} targets, not just those without commands.  This means you can
+do:@refill
+
+@example
+@group
+foo.o:
+        cc -c foo.c
+@end group
+@end example
+
+@noindent
+and Unix @code{make} will intuit that @file{foo.o} depends on
+@file{foo.c}.@refill
+
+We feel that such usage is broken.  The prerequisite properties of
+@code{make} are well-defined (for GNU @code{make}, at least),
+and doing such a thing simply does not fit the model.@refill
+
+@item
+GNU @code{make} does not include any built-in implicit rules for
+compiling or preprocessing EFL programs.  If we hear of anyone who is
+using EFL, we will gladly add them.
+
+@item
+It appears that in SVR4 @code{make}, a suffix rule can be specified with
+no commands, and it is treated as if it had empty commands
+(@pxref{Empty Commands}).  For example:
+
+@example
+.c.a:
+@end example
+
+@noindent
+will override the built-in @file{.c.a} suffix rule.
+
+We feel that it is cleaner for a rule without commands to always simply
+add to the prerequisite list for the target.  The above example can be
+easily rewritten to get the desired behavior in GNU @code{make}:
+
+@example
+.c.a: ;
+@end example
+
+@item
+Some versions of @code{make} invoke the shell with the @samp{-e} flag,
+except under @samp{-k} (@pxref{Testing, ,Testing the Compilation of a
+Program}).  The @samp{-e} flag tells the shell to exit as soon as any
+program it runs returns a nonzero status.  We feel it is cleaner to
+write each shell command line to stand on its own and not require this
+special treatment.
+@end itemize
+
+@comment The makefile standards are in a separate file that is also
+@comment included by standards.texi.
+@include make-stds.texi
+
+@node Quick Reference, Error Messages, Makefile Conventions, Top
+@appendix Quick Reference
+
+This appendix summarizes the directives, text manipulation functions,
+and special variables which GNU @code{make} understands.
+@xref{Special Targets}, @ref{Catalogue of Rules, ,Catalogue of Implicit Rules},
+and @ref{Options Summary, ,Summary of Options},
+for other summaries.
+
+Here is a summary of the directives GNU @code{make} recognizes:
+
+@table @code
+@item define @var{variable}
+@itemx endef
+
+Define a multi-line, recursively-expanded variable.@*
+@xref{Sequences}.
+
+@item ifdef @var{variable}
+@itemx ifndef @var{variable}
+@itemx ifeq (@var{a},@var{b})
+@itemx ifeq "@var{a}" "@var{b}"
+@itemx ifeq '@var{a}' '@var{b}'
+@itemx ifneq (@var{a},@var{b})
+@itemx ifneq "@var{a}" "@var{b}"
+@itemx ifneq '@var{a}' '@var{b}'
+@itemx else
+@itemx endif
+
+Conditionally evaluate part of the makefile.@*
+@xref{Conditionals}.
+
+@item include @var{file}
+@itemx -include @var{file}
+@itemx sinclude @var{file}
+
+Include another makefile.@*
+@xref{Include, ,Including Other Makefiles}.
+
+@item override @var{variable} = @var{value}
+@itemx override @var{variable} := @var{value}
+@itemx override @var{variable} += @var{value}
+@itemx override @var{variable} ?= @var{value}
+@itemx override define @var{variable}
+@itemx endef
+
+Define a variable, overriding any previous definition, even one from
+the command line.@*
+@xref{Override Directive, ,The @code{override} Directive}.
+
+@item export
+
+Tell @code{make} to export all variables to child processes by default.@*
+@xref{Variables/Recursion, , Communicating Variables to a Sub-@code{make}}.
+
+@item export @var{variable}
+@itemx export @var{variable} = @var{value}
+@itemx export @var{variable} := @var{value}
+@itemx export @var{variable} += @var{value}
+@itemx export @var{variable} ?= @var{value}
+@itemx unexport @var{variable}
+Tell @code{make} whether or not to export a particular variable to child
+processes.@*
+@xref{Variables/Recursion, , Communicating Variables to a Sub-@code{make}}.
+
+@item vpath @var{pattern} @var{path}
+Specify a search path for files matching a @samp{%} pattern.@*
+@xref{Selective Search, , The @code{vpath} Directive}.
+
+@item vpath @var{pattern}
+Remove all search paths previously specified for @var{pattern}.
+
+@item vpath
+Remove all search paths previously specified in any @code{vpath}
+directive.
+@end table
+
+Here is a summary of the text manipulation functions (@pxref{Functions}):
+
+@table @code
+@item $(subst @var{from},@var{to},@var{text})
+Replace @var{from} with @var{to} in @var{text}.@*
+@xref{Text Functions, , Functions for String Substitution and Analysis}.
+
+@item $(patsubst @var{pattern},@var{replacement},@var{text})
+Replace words matching @var{pattern} with @var{replacement} in @var{text}.@*
+@xref{Text Functions, , Functions for String Substitution and Analysis}.
+
+@item $(strip @var{string})
+Remove excess whitespace characters from @var{string}.@*
+@xref{Text Functions, , Functions for String Substitution and Analysis}.
+
+@item $(findstring @var{find},@var{text})
+Locate @var{find} in @var{text}.@*
+@xref{Text Functions, , Functions for String Substitution and Analysis}.
+
+@item $(filter @var{pattern}@dots{},@var{text})
+Select words in @var{text} that match one of the @var{pattern} words.@*
+@xref{Text Functions, , Functions for String Substitution and Analysis}.
+
+@item $(filter-out @var{pattern}@dots{},@var{text})
+Select words in @var{text} that @emph{do not} match any of the @var{pattern} words.@*
+@xref{Text Functions, , Functions for String Substitution and Analysis}.
+
+@item $(sort @var{list})
+Sort the words in @var{list} lexicographically, removing duplicates.@*
+@xref{Text Functions, , Functions for String Substitution and Analysis}.
+
+@item $(dir @var{names}@dots{})
+Extract the directory part of each file name.@*
+@xref{File Name Functions, ,Functions for File Names}.
+
+@item $(notdir @var{names}@dots{})
+Extract the non-directory part of each file name.@*
+@xref{File Name Functions, ,Functions for File Names}.
+
+@item $(suffix @var{names}@dots{})
+Extract the suffix (the last @samp{.} and following characters) of each file name.@*
+@xref{File Name Functions, ,Functions for File Names}.
+
+@item $(basename @var{names}@dots{})
+Extract the base name (name without suffix) of each file name.@*
+@xref{File Name Functions, ,Functions for File Names}.
+
+@item $(addsuffix @var{suffix},@var{names}@dots{})
+Append @var{suffix} to each word in @var{names}.@*
+@xref{File Name Functions, ,Functions for File Names}.
+
+@item $(addprefix @var{prefix},@var{names}@dots{})
+Prepend @var{prefix} to each word in @var{names}.@*
+@xref{File Name Functions, ,Functions for File Names}.
+
+@item $(join @var{list1},@var{list2})
+Join two parallel lists of words.@*
+@xref{File Name Functions, ,Functions for File Names}.
+
+@item $(word @var{n},@var{text})
+Extract the @var{n}th word (one-origin) of @var{text}.@*
+@xref{File Name Functions, ,Functions for File Names}.
+
+@item $(words @var{text})
+Count the number of words in @var{text}.@*
+@xref{File Name Functions, ,Functions for File Names}.
+
+@item $(wordlist @var{s},@var{e},@var{text})
+Returns the list of words in @var{text} from @var{s} to @var{e}.@*
+@xref{File Name Functions, ,Functions for File Names}.
+
+@item $(firstword @var{names}@dots{})
+Extract the first word of @var{names}.@*
+@xref{File Name Functions, ,Functions for File Names}.
+
+@item $(wildcard @var{pattern}@dots{})
+Find file names matching a shell file name pattern (@emph{not} a
+@samp{%} pattern).@*
+@xref{Wildcard Function, ,The Function @code{wildcard}}.
+
+@item $(error @var{text}@dots{})
+
+When this function is evaluated, @code{make} generates a fatal error
+with the message @var{text}.@*
+@xref{Make Control Functions, ,Functions That Control Make}.
+
+@item $(warning @var{text}@dots{})
+
+When this function is evaluated, @code{make} generates a warning with
+the message @var{text}.@*
+@xref{Make Control Functions, ,Functions That Control Make}.
+
+@item $(shell @var{command})
+
+Execute a shell command and return its output.@*
+@xref{Shell Function, , The @code{shell} Function}.
+
+@item $(origin @var{variable})
+
+Return a string describing how the @code{make} variable @var{variable} was
+defined.@*
+@xref{Origin Function, , The @code{origin} Function}.
+
+@item $(foreach @var{var},@var{words},@var{text})
+
+Evaluate @var{text} with @var{var} bound to each word in @var{words},
+and concatenate the results.@*
+@xref{Foreach Function, ,The @code{foreach} Function}.
+
+@item $(call @var{var},@var{param},@dots{})
+
+Evaluate the variable @var{var} replacing any references to @code{$(1)},
+@code{$(2)} with the first, second, etc. @var{param} values.@*
+@xref{Call Function, ,The @code{call} Function}.
+@end table
+
+Here is a summary of the automatic variables.
+@xref{Automatic, ,Automatic Variables},
+for full information.
+
+@table @code
+@item $@@
+The file name of the target.
+
+@item $%
+The target member name, when the target is an archive member.
+
+@item $<
+The name of the first prerequisite.
+
+@item $?
+The names of all the prerequisites that are
+newer than the target, with spaces between them.
+For prerequisites which are archive members, only
+the member named is used (@pxref{Archives}).
+
+@item $^
+@itemx $+
+The names of all the prerequisites, with spaces between them.  For
+prerequisites which are archive members, only the member named is used
+(@pxref{Archives}).  The value of @code{$^} omits duplicate
+prerequisites, while @code{$+} retains them and preserves their order.
+
+@item $*
+The stem with which an implicit rule matches
+(@pxref{Pattern Match, ,How Patterns Match}).
+
+@item $(@@D)
+@itemx $(@@F)
+The directory part and the file-within-directory part of @code{$@@}.
+
+@item $(*D)
+@itemx $(*F)
+The directory part and the file-within-directory part of @code{$*}.
+
+@item $(%D)
+@itemx $(%F)
+The directory part and the file-within-directory part of @code{$%}.
+
+@item $(<D)
+@itemx $(<F)
+The directory part and the file-within-directory part of @code{$<}.
+
+@item $(^D)
+@itemx $(^F)
+The directory part and the file-within-directory part of @code{$^}.
+
+@item $(+D)
+@itemx $(+F)
+The directory part and the file-within-directory part of @code{$+}.
+
+@item $(?D)
+@itemx $(?F)
+The directory part and the file-within-directory part of @code{$?}.
+@end table
+
+These variables are used specially by GNU @code{make}:
+
+@table @code
+@item MAKEFILES
+
+Makefiles to be read on every invocation of @code{make}.@*
+@xref{MAKEFILES Variable, ,The Variable @code{MAKEFILES}}.
+
+@item VPATH
+
+Directory search path for files not found in the current directory.@*
+@xref{General Search, , @code{VPATH} Search Path for All Prerequisites}.
+
+@item SHELL
+
+The name of the system default command interpreter, usually @file{/bin/sh}.
+You can set @code{SHELL} in the makefile to change the shell used to run
+commands.  @xref{Execution, ,Command Execution}.
+
+@item MAKESHELL
+
+On MS-DOS only, the name of the command interpreter that is to be used
+by @code{make}. This value takes precedence over the value of
+@code{SHELL}.  @xref{Execution, ,MAKESHELL variable}.
+
+@item MAKE
+
+The name with which @code{make} was invoked.
+Using this variable in commands has special meaning.
+@xref{MAKE Variable, ,How the @code{MAKE} Variable Works}.
+
+@item MAKELEVEL
+
+The number of levels of recursion (sub-@code{make}s).@*
+@xref{Variables/Recursion}.
+
+@item MAKEFLAGS
+
+The flags given to @code{make}.  You can set this in the environment or
+a makefile to set flags.@*
+@xref{Options/Recursion, ,Communicating Options to a Sub-@code{make}}.
+
+It is @emph{never} appropriate to use @code{MAKEFLAGS} directly on a
+command line: its contents may not be quoted correctly for use in the
+shell.  Always allow recursive @code{make}'s to obtain these values
+through the environment from its parent.
+
+@item MAKECMDGOALS
+
+The targets given to @code{make} on the command line.  Setting this
+variable has no effect on the operation of @code{make}.@*
+@xref{Goals, ,Arguments to Specify the Goals}.
+
+@item CURDIR
+
+Set to the pathname of the current working directory (after all
+@code{-C} options are processed, if any).  Setting this variable has no
+effect on the operation of @code{make}.@*
+@xref{Recursion, ,Recursive Use of @code{make}}.
+
+@item SUFFIXES
+
+The default list of suffixes before @code{make} reads any makefiles.
+
+@item .LIBPATTERNS
+Defines the naming of the libraries @code{make} searches for, and their
+order.@*
+@xref{Libraries/Search, ,Directory Search for Link Libraries}.
+@end table
+
+@node Error Messages, Complex Makefile, Quick Reference, Top
+@comment  node-name,  next,  previous,  up
+@appendix Errors Generated by Make
+
+Here is a list of the more common errors you might see generated by
+@code{make}, and some information about what they mean and how to fix
+them.
+
+Sometimes @code{make} errors are not fatal, especially in the presence
+of a @code{-} prefix on a command script line, or the @code{-k} command
+line option.  Errors that are fatal are prefixed with the string
+@code{***}.
+
+Error messages are all either prefixed with the name of the program
+(usually @samp{make}), or, if the error is found in a makefile, the name
+of the file and linenumber containing the problem.
+
+In the table below, these common prefixes are left off.
+
+@table @samp
+
+@item [@var{foo}] Error @var{NN}
+@itemx [@var{foo}] @var{signal description}
+These errors are not really @code{make} errors at all.  They mean that a
+program that @code{make} invoked as part of a command script returned a
+non-0 error code (@samp{Error @var{NN}}), which @code{make} interprets
+as failure, or it exited in some other abnormal fashion (with a
+signal of some type).  @xref{Errors, ,Errors in Commands}.
+
+If no @code{***} is attached to the message, then the subprocess failed
+but the rule in the makefile was prefixed with the @code{-} special
+character, so @code{make} ignored the error.
+
+@item missing separator.  Stop.
+@itemx missing separator (did you mean TAB instead of 8 spaces?).  Stop.
+This means that @code{make} could not understand much of anything about
+the command line it just read.  GNU @code{make} looks for various kinds
+of separators (@code{:}, @code{=}, TAB characters, etc.) to help it
+decide what kind of commandline it's seeing.  This means it couldn't
+find a valid one.
+
+One of the most common reasons for this message is that you (or perhaps
+your oh-so-helpful editor, as is the case with many MS-Windows editors)
+have attempted to indent your command scripts with spaces instead of a
+TAB character.  In this case, @code{make} will use the second form of
+the error above.  Remember that every line in the command script must
+begin with a TAB character.  Eight spaces do not count.  @xref{Rule
+Syntax}.
+
+@item commands commence before first target.  Stop.
+@itemx missing rule before commands.  Stop.
+This means the first thing in the makefile seems to be part of a command
+script: it begins with a TAB character and doesn't appear to be a legal
+@code{make} command (such as a variable assignment).  Command scripts
+must always be associated with a target.
+
+The second form is generated if the line has a semicolon as the first
+non-whitespace character; @code{make} interprets this to mean you left
+out the "target: prerequisite" section of a rule.  @xref{Rule Syntax}.
+
+@item No rule to make target `@var{xxx}'.
+@itemx No rule to make target `@var{xxx}', needed by `@var{yyy}'.
+This means that @code{make} decided it needed to build a target, but
+then couldn't find any instructions in the makefile on how to do that,
+either explicit or implicit (including in the default rules database).
+
+If you want that file to be built, you will need to add a rule to your
+makefile describing how that target can be built.  Other possible
+sources of this problem are typos in the makefile (if that filename is
+wrong) or a corrupted source tree (if that file is not supposed to be
+built, but rather only a prerequisite).
+
+@item No targets specified and no makefile found.  Stop.
+@itemx No targets.  Stop.
+The former means that you didn't provide any targets to be built on the
+command line, and @code{make} couldn't find any makefiles to read in.
+The latter means that some makefile was found, but it didn't contain any
+default target and none was given on the command line.  GNU @code{make}
+has nothing to do in these situations.
+@xref{Makefile Arguments, ,Arguments to Specify the Makefile}.@refill
+
+@item Makefile `@var{xxx}' was not found.
+@itemx Included makefile `@var{xxx}' was not found.
+A makefile specified on the command line (first form) or included
+(second form) was not found.
+
+@item warning: overriding commands for target `@var{xxx}'
+@itemx warning: ignoring old commands for target `@var{xxx}'
+GNU @code{make} allows commands to be specified only once per target
+(except for double-colon rules).  If you give commands for a target
+which already has been defined to have commands, this warning is issued
+and the second set of commands will overwrite the first set.
+@xref{Multiple Rules, ,Multiple Rules for One Target}.
+
+@item Circular @var{xxx} <- @var{yyy} dependency dropped.
+This means that @code{make} detected a loop in the dependency graph:
+after tracing the prerequisite @var{yyy} of target @var{xxx}, and its
+prerequisites, etc., one of them depended on @var{xxx} again.
+
+@item Recursive variable `@var{xxx}' references itself (eventually).  Stop.
+This means you've defined a normal (recursive) @code{make} variable
+@var{xxx} that, when it's expanded, will refer to itself (@var{xxx}).
+This is not allowed; either use simply-expanded variables (@code{:=}) or
+use the append operator (@code{+=}).  @xref{Using Variables, ,How to Use
+Variables}.
+
+@item Unterminated variable reference.  Stop.
+This means you forgot to provide the proper closing parenthesis
+or brace in your variable or function reference.
+
+@item insufficient arguments to function `@var{xxx}'.  Stop.
+This means you haven't provided the requisite number of arguments for
+this function.  See the documentation of the function for a description
+of its arguments.  @xref{Functions, ,Functions for Transforming Text}.
+
+@item missing target pattern.  Stop.
+@itemx multiple target patterns.  Stop.
+@itemx target pattern contains no `%'.  Stop.
+@itemx mixed implicit and static pattern rules.  Stop.
+These are generated for malformed static pattern rules.  The first means
+there's no pattern in the target section of the rule; the second means
+there are multiple patterns in the target section; the third means
+the target doesn't contain a pattern character (@code{%}); and the
+fourth means that all three parts of the static pattern rule contain
+pattern characters (@code{%})--only the first two parts should.
+@xref{Static Usage, ,Syntax of Static Pattern Rules}.
+
+@item warning: -jN forced in submake: disabling jobserver mode.
+This warning and the next are generated if @code{make} detects error
+conditions related to parallel processing on systems where
+sub-@code{make}s can communicate (@pxref{Options/Recursion,
+,Communicating Options to a Sub-@code{make}}).  This warning is
+generated if a recursive invocation of a @code{make} process is forced
+to have @samp{-j@var{N}} in its argument list (where @var{N} is greater
+than one).  This could happen, for example, if you set the @code{MAKE}
+environment variable to @samp{make -j2}.  In this case, the
+sub-@code{make} doesn't communicate with other @code{make} processes and
+will simply pretend it has two jobs of its own.
+
+@item warning: jobserver unavailable: using -j1.  Add `+' to parent make rule.
+In order for @code{make} processes to communicate, the parent will pass
+information to the child.  Since this could result in problems if the
+child process isn't actually a @code{make}, the parent will only do this
+if it thinks the child is a @code{make}.  The parent uses the normal
+algorithms to determine this (@pxref{MAKE Variable, ,How the @code{MAKE}
+Variable Works}).  If the makefile is constructed such that the parent
+doesn't know the child is a @code{make} process, then the child will
+receive only part of the information necessary.  In this case, the child
+will generate this warning message and proceed with its build in a
+sequential manner.
+
+@end table
+
+@node Complex Makefile, GNU Free Documentation License, Error Messages, Top
+@appendix Complex Makefile Example
+
+Here is the makefile for the GNU @code{tar} program.  This is a
+moderately complex makefile.
+
+Because it is the first target, the default goal is @samp{all}.  An
+interesting feature of this makefile is that @file{testpad.h} is a
+source file automatically created by the @code{testpad} program,
+itself compiled from @file{testpad.c}.
+
+If you type @samp{make} or @samp{make all}, then @code{make} creates
+the @file{tar} executable, the @file{rmt} daemon that provides
+remote tape access, and the @file{tar.info} Info file.
+
+If you type @samp{make install}, then @code{make} not only creates
+@file{tar}, @file{rmt}, and @file{tar.info}, but also installs
+them.
+
+If you type @samp{make clean}, then @code{make} removes the @samp{.o}
+files, and the @file{tar}, @file{rmt}, @file{testpad},
+@file{testpad.h}, and @file{core} files.
+
+If you type @samp{make distclean}, then @code{make} not only removes
+the same files as does @samp{make clean} but also the
+@file{TAGS}, @file{Makefile}, and @file{config.status} files.
+(Although it is not evident, this makefile (and
+@file{config.status}) is generated by the user with the
+@code{configure} program, which is provided in the @code{tar}
+distribution, but is not shown here.)
+
+If you type @samp{make realclean}, then @code{make} removes the same
+files as does @samp{make distclean} and also removes the Info files
+generated from @file{tar.texinfo}.
+
+In addition, there are targets @code{shar} and @code{dist} that create
+distribution kits.
+
+@example
+@group
+# Generated automatically from Makefile.in by configure.
+# Un*x Makefile for GNU tar program.
+# Copyright (C) 1991 Free Software Foundation, Inc.
+@end group
+
+@group
+# This program is free software; you can redistribute
+# it and/or modify it under the terms of the GNU
+# General Public License @dots{}
+@dots{}
+@dots{}
+@end group
+
+SHELL = /bin/sh
+
+#### Start of system configuration section. ####
+
+srcdir = .
+
+@group
+# If you use gcc, you should either run the
+# fixincludes script that comes with it or else use
+# gcc with the -traditional option.  Otherwise ioctl
+# calls will be compiled incorrectly on some systems.
+CC = gcc -O
+YACC = bison -y
+INSTALL = /usr/local/bin/install -c
+INSTALLDATA = /usr/local/bin/install -c -m 644
+@end group
+
+# Things you might add to DEFS:
+# -DSTDC_HEADERS        If you have ANSI C headers and
+#                       libraries.
+# -DPOSIX               If you have POSIX.1 headers and
+#                       libraries.
+# -DBSD42               If you have sys/dir.h (unless
+#                       you use -DPOSIX), sys/file.h,
+#                       and st_blocks in `struct stat'.
+# -DUSG                 If you have System V/ANSI C
+#                       string and memory functions
+#                       and headers, sys/sysmacros.h,
+#                       fcntl.h, getcwd, no valloc,
+#                       and ndir.h (unless
+#                       you use -DDIRENT).
+# -DNO_MEMORY_H         If USG or STDC_HEADERS but do not
+#                       include memory.h.
+# -DDIRENT              If USG and you have dirent.h
+#                       instead of ndir.h.
+# -DSIGTYPE=int         If your signal handlers
+#                       return int, not void.
+# -DNO_MTIO             If you lack sys/mtio.h
+#                       (magtape ioctls).
+# -DNO_REMOTE           If you do not have a remote shell
+#                       or rexec.
+# -DUSE_REXEC           To use rexec for remote tape
+#                       operations instead of
+#                       forking rsh or remsh.
+# -DVPRINTF_MISSING     If you lack vprintf function
+#                       (but have _doprnt).
+# -DDOPRNT_MISSING      If you lack _doprnt function.
+#                       Also need to define
+#                       -DVPRINTF_MISSING.
+# -DFTIME_MISSING       If you lack ftime system call.
+# -DSTRSTR_MISSING      If you lack strstr function.
+# -DVALLOC_MISSING      If you lack valloc function.
+# -DMKDIR_MISSING       If you lack mkdir and
+#                       rmdir system calls.
+# -DRENAME_MISSING      If you lack rename system call.
+# -DFTRUNCATE_MISSING   If you lack ftruncate
+#                       system call.
+# -DV7                  On Version 7 Unix (not
+#                       tested in a long time).
+# -DEMUL_OPEN3          If you lack a 3-argument version
+#                       of open, and want to emulate it
+#                       with system calls you do have.
+# -DNO_OPEN3            If you lack the 3-argument open
+#                       and want to disable the tar -k
+#                       option instead of emulating open.
+# -DXENIX               If you have sys/inode.h
+#                       and need it 94 to be included.
+
+DEFS =  -DSIGTYPE=int -DDIRENT -DSTRSTR_MISSING \
+        -DVPRINTF_MISSING -DBSD42
+# Set this to rtapelib.o unless you defined NO_REMOTE,
+# in which case make it empty.
+RTAPELIB = rtapelib.o
+LIBS =
+DEF_AR_FILE = /dev/rmt8
+DEFBLOCKING = 20
+
+@group
+CDEBUG = -g
+CFLAGS = $(CDEBUG) -I. -I$(srcdir) $(DEFS) \
+        -DDEF_AR_FILE=\"$(DEF_AR_FILE)\" \
+        -DDEFBLOCKING=$(DEFBLOCKING)
+LDFLAGS = -g
+@end group
+
+@group
+prefix = /usr/local
+# Prefix for each installed program,
+# normally empty or `g'.
+binprefix =
+
+# The directory to install tar in.
+bindir = $(prefix)/bin
+
+# The directory to install the info files in.
+infodir = $(prefix)/info
+@end group
+
+#### End of system configuration section. ####
+
+SRC1 =  tar.c create.c extract.c buffer.c \
+        getoldopt.c update.c gnu.c mangle.c
+SRC2 =  version.c list.c names.c diffarch.c \
+        port.c wildmat.c getopt.c
+SRC3 =  getopt1.c regex.c getdate.y
+SRCS =  $(SRC1) $(SRC2) $(SRC3)
+OBJ1 =  tar.o create.o extract.o buffer.o \
+        getoldopt.o update.o gnu.o mangle.o
+OBJ2 =  version.o list.o names.o diffarch.o \
+        port.o wildmat.o getopt.o
+OBJ3 =  getopt1.o regex.o getdate.o $(RTAPELIB)
+OBJS =  $(OBJ1) $(OBJ2) $(OBJ3)
+@group
+AUX =   README COPYING ChangeLog Makefile.in  \
+        makefile.pc configure configure.in \
+        tar.texinfo tar.info* texinfo.tex \
+        tar.h port.h open3.h getopt.h regex.h \
+        rmt.h rmt.c rtapelib.c alloca.c \
+        msd_dir.h msd_dir.c tcexparg.c \
+        level-0 level-1 backup-specs testpad.c
+@end group
+
+all:    tar rmt tar.info
+
+@group
+tar:    $(OBJS)
+        $(CC) $(LDFLAGS) -o $@@ $(OBJS) $(LIBS)
+@end group
+
+@group
+rmt:    rmt.c
+        $(CC) $(CFLAGS) $(LDFLAGS) -o $@@ rmt.c
+@end group
+
+@group
+tar.info: tar.texinfo
+        makeinfo tar.texinfo
+@end group
+
+@group
+install: all
+        $(INSTALL) tar $(bindir)/$(binprefix)tar
+        -test ! -f rmt || $(INSTALL) rmt /etc/rmt
+        $(INSTALLDATA) $(srcdir)/tar.info* $(infodir)
+@end group
+
+@group
+$(OBJS): tar.h port.h testpad.h
+regex.o buffer.o tar.o: regex.h
+# getdate.y has 8 shift/reduce conflicts.
+@end group
+
+@group
+testpad.h: testpad
+        ./testpad
+@end group
+
+@group
+testpad: testpad.o
+        $(CC) -o $@@ testpad.o
+@end group
+
+@group
+TAGS:   $(SRCS)
+        etags $(SRCS)
+@end group
+
+@group
+clean:
+        rm -f *.o tar rmt testpad testpad.h core
+@end group
+
+@group
+distclean: clean
+        rm -f TAGS Makefile config.status
+@end group
+
+@group
+realclean: distclean
+        rm -f tar.info*
+@end group
+
+@group
+shar: $(SRCS) $(AUX)
+        shar $(SRCS) $(AUX) | compress \
+          > tar-`sed -e '/version_string/!d' \
+                     -e 's/[^0-9.]*\([0-9.]*\).*/\1/' \
+                     -e q
+                     version.c`.shar.Z
+@end group
+
+@group
+dist: $(SRCS) $(AUX)
+        echo tar-`sed \
+             -e '/version_string/!d' \
+             -e 's/[^0-9.]*\([0-9.]*\).*/\1/' \
+             -e q
+             version.c` > .fname
+        -rm -rf `cat .fname`
+        mkdir `cat .fname`
+        ln $(SRCS) $(AUX) `cat .fname`
+        tar chZf `cat .fname`.tar.Z `cat .fname`
+        -rm -rf `cat .fname` .fname
+@end group
+
+@group
+tar.zoo: $(SRCS) $(AUX)
+        -rm -rf tmp.dir
+        -mkdir tmp.dir
+        -rm tar.zoo
+        for X in $(SRCS) $(AUX) ; do \
+            echo $$X ; \
+            sed 's/$$/^M/' $$X \
+            > tmp.dir/$$X ; done
+        cd tmp.dir ; zoo aM ../tar.zoo *
+        -rm -rf tmp.dir
+@end group
+@end example
+
+@raisesections
+@include fdl.texi
+@lowersections
+
+@node Concept Index, Name Index, GNU Free Documentation License, Top
+@unnumbered Index of Concepts
+
+@printindex cp
+
+@node Name Index,  , Concept Index, Top
+@unnumbered Index of Functions, Variables, & Directives
+
+@printindex fn
+
+@summarycontents
+@contents
+@bye